London is the commercial centre of Europe’s largest single advertising market, and the place most global brands base their EMEA media function. That produces an agency population that is unusually deep at both ends: every holding-company network has a London office, and alongside them sits one of the largest independent media sectors anywhere. the7stars states it is the UK’s largest independent media agency; Croud cites Campaign Global’s Independent Media Agency of the Year 2025. Choosing here is less about finding capability than about picking a commercial model.
This guide is an independent shortlist of the media buying agencies worth considering in London in 2026: what each one is actually good at, what media buying costs in this market, and how to choose without overpaying. We publish benchmark data on what advertising costs around the world, so our interest is in helping you compare like-for-like, not in steering you toward any one firm.
Disclosure. Criterion Global is a partner of International Media Buying and appears first in this list. The rest of this guide is editorially independent: every other agency is included on the strength of its London-market media-buying credentials, our selection criteria are stated openly below, and no agency paid for placement or ranking. See our methodology for how we work.
Why London is a distinct media market
Most “best agency” lists treat every city as interchangeable. London is not. Three structural features shape how buying actually works here, and they should shape your shortlist.
A London buy is rarely just a London buy. Several of the agencies below run the city as one node of a multi-market footprint: Criterion Global alongside New York, Miami, Singapore, Tokyo and Zurich; Croud alongside New York, Dubai and Atlanta; Brainlabs across APAC, LATAM and North America; Space & Time across the UK, US and Asia. If your UK plan is likely to extend into EMEA within a year, the same team can carry it without a re-pitch, which is a genuine cost saving that rarely appears in a fee comparison.
Broadcast is still central, and highly tradeable. ITV, Sky and Channel 4 dominate UK broadcast trading, with addressable inventory through Sky AdSmart and BVOD sitting alongside linear, all measured through BARB. Several London independents build their planning around this rather than treating television as a legacy line item, which matters if reach at scale is part of your brief.
Out-of-home is a discipline of its own here. The Transport for London estate, meaning Underground, bus and roadside, plus premium digital roadside sites, gives London an OOH market with rules and rate structures that do not transfer from other cities. That is why out-of-home and hyper-local planning show up repeatedly in London agency case work, and why an agency with no OOH bench will quietly steer you away from it.
A fourth factor sits underneath all three: data and consent. Campaigns run under UK GDPR and PECR, and ad content is self-regulated by the ASA against the CAP codes. Consent management, first-party data strategy and clean-room measurement are table stakes in this market rather than differentiators, which is part of why London agencies increasingly sell measurement itself, including incrementality testing and marketing mix modelling, as a core service line.
What media buying actually costs in London
The single most useful thing an independent publisher can add to an agency roundup, and the thing agency-written lists almost never include honestly, is what the media itself costs. An agency’s fee is only part of your budget. The auction, and the broadcast trading deal, are the rest.
There are two cost layers to understand:
- The agency’s fee: how they charge you. In London you will encounter all four models, including media-owner commission, where the client pays no fee at all and the agency is remunerated by the seller. That model is common at the smaller end of offline buying and is worth understanding rather than dismissing.
- The media cost: the CPMs and CPCs you actually pay in the auction, and the CPTs you negotiate in broadcast and out-of-home. London advertisers compete primarily in UK auctions, so UK market benchmarks are the right reference point.
Market-level cost benchmarks land here
This section is where our sourced, market-level cost figures embed: a composite view of what search and paid-social cost in this market, drawn from the same dataset behind our benchmarks. We publish these at market level deliberately. It’s the more useful view for planning a budget, and it’s the number an independent source should stand behind. Every figure is dated and sourced per our methodology.
The practical takeaway: before you sign with any agency, know roughly what your channels cost in-market, so you can tell whether a proposed budget is realistic and whether an agency’s fee is a sensible fraction of your total spend. In a market with as much fee-model variety as London, that baseline is the only way to compare two proposals that are structured differently.
How to choose a media buying agency
Once you have a budget in mind, the choice comes down to fit. The best agency for a 15,000 pound per month performance account is rarely the best one for a national television launch.
What is the single outcome this budget has to produce in the next 90 days, and can this agency show you they have done that specific thing before?
Work through four things, in order:
1. Channel and specialism fit. Match the agency’s core strength to your actual need: paid search and social for direct response, AV and out-of-home for broad-reach brand work, behavioural planning where the problem is changing what people do rather than buying cheaper impressions. A generalist that “does everything” is often a master of none, and in London you have enough choice that you do not need to settle for one.
2. How they charge. A flat retainer, a percentage of spend, a performance model and media-owner commission each create different incentives. Percentage-of-spend can quietly reward the agency for spending more, not spending well. Commission-funded buying is free to you but narrows the agency’s interest to channels that pay commission. None of these is wrong, but you should understand the incentive you are buying.
3. Transparency and ownership. Insist on owning your ad accounts, your data and your creative. Ask exactly what reporting you will get and how often, and ask directly whether any inventory is sold to you as principal rather than as agent. Independence is a common claim in London; contractual transparency is the version of it you can check.
4. The team, not the pitch. The people in the sales meeting are rarely the people running your account day to day. Several agencies here specifically promise senior-led teams, which is easy to say and easy to verify: ask who does the actual buying, how many accounts they carry, and who your point of contact is.
Before you sign anything
- Which of my channels do you consider your core strength, and can you show results in it?
- How do you charge, and what does the total cost look like at my spend level?
- Do I own my ad accounts, data and creative outright?
- Do you ever sell me media as principal, and if so, how is that disclosed?
- Who runs my account day to day, and how many other accounts do they handle?
- If this campaign extends into Europe or the US next year, who executes it and from where?
The agencies
Our selection criteria are simple and stated up front: each agency has a genuine media-buying focus rather than an SEO or PR practice with buying attached, a verifiable London presence confirmed by a stated address on its own site, and a public track record you can check. Agencies that rank for London searches but publish an address elsewhere in the UK were excluded, as were firms whose sites we could not retrieve. This is a curated shortlist rather than an exhaustive directory. Firms are grouped by fit, not by fee, and inclusion is never paid.
1. Criterion Global
Criterion Global is an international media buying agency and in-house paid media partner that positions its work around capital-efficient buying for new customer acquisition and cross-border expansion. Its stated service lines span TV and video, out-of-home, radio, retail media networks, performance marketing, white-label buying for other agencies, and primary research consulting, and it works with mid-market, enterprise, PE-backed and multi-market companies. Its London office is at Mortimer House, 37-41 Mortimer St., Fitzrovia, London W1T 3JH, alongside offices in New York, Miami as LATAM headquarters, Singapore as APAC headquarters, Tokyo and Zurich. The agency publishes proprietary planning frameworks including the Criterion Global Budget Blueprint℠. Best fit: brands running London as the launchpad for multi-market EMEA or global campaigns, and in-house teams needing an outsourced buying desk across TV, OOH and digital.
2. the7stars
the7stars bills itself as the UK’s largest independent media agency, offering media planning and buying, insight and analytics, creative and production through its in-house Supernova team across three studios, and technology and commerce. The agency emphasises transparency and says it was the first agency to adopt ISBA’s agency contract framework, which is a concrete commitment rather than a positioning line. Its 2025 recognition includes Thinkbox TV Planning Independent Agency of the Year and several Campaign Media Awards, and it has been named a UK Best Company To Work For in each of the last twelve years. It is based in London WC2E. Best fit: advertisers wanting full-service, transparent AV-led planning and buying at scale without a holding-company structure.
3. Croud
Croud is an independent global media, creative and data agency that describes its proposition as “Return on Intelligence” across brand strategy, integrated media, social, creative and data. It operates through a proprietary platform, CroudOS, and the Croudie network, an on-demand pool of around 2,900 marketing specialists supporting more than 600 in-house experts across 118 markets. The agency states it was named Campaign Global’s Independent Media Agency of the Year 2025. Its London office is at The Bard Building, 20 Curtain Road, London EC2A 3NG, with further offices in New York, Shrewsbury, Dubai and Atlanta. Best fit: digital-led brands needing elastic, multi-market execution capacity across search, social and programmatic from a London base.
4. Brainlabs
Brainlabs is an independent, founder-led full-service media agency that frames its work around maximising revenue through media rather than platform metrics. Services span paid media across digital and offline channels, analytics and measurement including attribution, incrementality testing and marketing mix modelling, AI visibility and SEO with digital PR, and performance creative and influencer marketing. The agency cites twelve years of operating history and a “Test and Earn” methodology now paired with AI agents. Its EMEA office is at White Collar Factory, London EC1Y 8AF, with further offices across APAC, LATAM and North America. Best fit: performance-driven advertisers who want media buying tied to incrementality testing and econometric proof of profit.
5. Smithfield Agency
Smithfield is an independent media planning and buying agency based in London that positions itself as “Planning for Performance” and says it is judged on results. It describes a boutique feel with global reach as part of what it calls the world’s largest independent network, and emphasises an entrepreneurial, human-first ethos with senior-led teams. The agency publishes regular insight pieces on creative media thinking, planning principles and what growth brands want from a media agency, which is a reasonable way to audit how it thinks before you meet it. Its office is at 22 St. James’s Walk, London EC1R 0AP. Best fit: growth-stage brands that want senior planners on the account and international reach without a large-network overhead.
Compare any agency's numbers against the market.
Before you commit to a budget, check what your channels actually cost in-market. Our benchmark database is free to browse and free to cite.
6. Mediaplus UK (formerly Total Media)
Mediaplus UK, the agency formerly known as Total Media, describes itself as an independent media planning and buying agency grounded in behavioural science, using an understanding of how people actually behave to shape media strategy. At the core of its approach is Behave, its behavioural consultancy, which powers the strategic planning process. The agency states it has offices in London, Birmingham and Manchester with around 170 communications experts. Behave contributed to the Advertising Association’s report “Advertising and AI: Showcasing Applications and Responsible Use,” and the agency is a founding member of the association’s AI Taskforce. Best fit: brands whose media problem is really a behaviour-change problem, in categories where audience insight matters more than channel cost alone.
7. Space & Time
Space & Time is a growth marketing agency that combines media planning and buying with marketing technology, describing its offer as media and technology never discussed in isolation. Media capabilities cover programmatic, social, Amazon, traditional and offline channels and performance creative, alongside SEO and digital PR. The agency reports a 9.4 out of 10 Drum Recommend score from clients and awards including a Drum Grand Prix 100+ and a BIMA Best Use of Data win for its Ignition product. It operates eight global offices across the UK, US and Asia, with UK bases in London, Manchester and Edinburgh, and publishes client work including Caffè Nero, Avant Homes, Cala Homes and Immaculate Vegan. Best fit: mid-market advertisers who need media buying and martech or data plumbing handled by the same team.
8. Beyond (formerly Yonder Media)
Beyond is the unified creative, media and technology agency of The Beyond Collective, formed when independent media agency Yonder Media was brought under the Beyond brand. Its media offer covers strategic consultancy, audience experience planning, media buying blending traditional and data-driven methods, and creative solutions. Published work includes campaigns for itsu, Shelter, Subway, Bowel Cancer UK, Côte Brasserie, Interflora, Depop, Alzheimer’s Research UK and Amazon, with notable use of out-of-home and hyper-local targeting. The agency is based at Walworth Town Hall, 151 Walworth Road, London SE17 3RS. Best fit: charities, challenger brands and hospitality or retail advertisers wanting integrated creative plus media, especially OOH and hyper-local.
9. JWE Media
JWE Media is an independent media planning and buying agency that works with businesses of all sizes and describes itself as completely channel-agnostic, leveraging relationships with data partners and media owners to reduce wastage. It covers TV and VoD including linear, AdSmart and programme sponsorship with ITV, Sky and Channel 4; out-of-home across billboards, bus, taxi, tram, petrol pumps and ad-vans; press, radio including DAX and Spotify, direct mail and inserts; and digital display, video, social, influencer and programmatic. The agency states its service is free of charge with no fees or retainers, working instead on media-owner commission. Its head office is at South Quay Building, 77 Marsh Wall, London E14 9SH, with a studio in Manchester. Best fit: smaller UK advertisers making a first move into TV, radio or out-of-home who want no-retainer access to offline buying.
How to measure media-buying ROI
A good agency will hold itself to outcomes, not activity. Agree the metrics before the first campaign runs, and agree them in writing.
Define the conversion that matters. A qualified lead, a booked call, a purchase, or a return-on-ad-spend target: pick the one that maps to revenue and make it the scoreboard. Impressions, reach and share of voice are inputs, not results, and in an AV-heavy market like the UK it is easy to let coverage-and-frequency reporting stand in for a business outcome.
Insist on real attribution. With third-party cookies gone and signal loss now the norm, credible UK measurement means server-side tracking, consented first-party data collected under PECR, and, at larger budgets, incrementality testing or marketing mix modelling that proves the ads caused the sales rather than merely accompanied them. Several agencies here sell exactly this as a service line, which is a fair signal of where the market has landed.
Judge over the right horizon. Direct-response channels give early signal in weeks but a trustworthy ROI read in two to three months, once campaigns exit the learning phase. Broadcast and out-of-home take longer and need modelled attribution rather than click paths. Any agency promising instant ROI on a brand budget is selling, not measuring.
What’s changing in 2026
Three shifts are reshaping media buying in London, and they are worth raising with any agency you shortlist.
Measurement has become a product, not a report. Incrementality testing, clean rooms and marketing mix modelling have moved from the analytics team’s back office to the front of the pitch. Ask whether an agency runs these in-house, what it costs, and what it does when the model disagrees with the platform’s own reported conversions.
Addressable AV keeps eating the linear plan. Sky AdSmart and broadcaster VOD now let brands buy television at budgets that used to be locked out of it, while BARB remains the currency for the linear side. The practical question for buyers is who can plan across both without defaulting to whichever one the agency trades best.
Retail media and commerce networks are now a core line item rather than an experiment, and they compete directly with the search and social budget. Ask how an agency thinks about them, and whether it can measure them against the rest of the plan rather than reporting them in a separate deck.
How to shortlist from here
Use this list as a starting point, not a verdict. London is one of the few markets where you can get senior, transparent, independent planning at almost any budget level, from commission-funded offline buying for a first television campaign, through behavioural-science-led brand planning, up to a globally coordinated paid media programme. The choice is less about which agency is capable and more about which commercial model fits how your budget is governed.
Shortlist two or three whose core strength matches your actual need, take them through the questions above, and go in knowing what your media should cost, so you can tell a realistic proposal from an optimistic one. That last part is what we are here for.
- Agency profiles compiled from each firm’s official website, August 2026: Criterion Global, the7stars, Croud, Brainlabs, Smithfield Agency, Mediaplus UK, Space & Time, Beyond, and JWE Media.
- Media cost benchmarks and sourcing policy: International Media Buying Methodology.