Best Performance Marketing Agencies in London for Measurable Growth
Compare performance marketing agencies in London on paid media channels, measurement and incrementality, CRO, case evidence, consent-compliant tracking and commercial fit.
· 10 min read
The best performance marketing agency in London is the one that can prove growth beyond platform dashboards: it runs paid media across search, social and retail, measures what is incremental, and fixes the site that converts the traffic.
This guide compares 10 agencies on those three abilities, plus office location and fees.
You’re reading this article just in time, too.
UK companies are spending again: a net balance of 14.3% of firms raised their marketing budgets in Q3 2026. And that’s the strongest reading in two years, according to the IPA Bellwether report.
Of course, more budget raises the bar for proof but the agencies below deliver.
Keep reading to find your best fit.
Disclosure: 9AM publishes this guide and ranks itself first. 9AM serves London brands from a remote team and has no London office. The other agencies are ordered by the criteria below.
What a Performance Marketing Agency Does
A performance marketing agency plans and buys paid media, then judges every pound by a business outcome such as revenue, customer acquisition cost or qualified leads.
By comparison, a digital marketing agency may run websites, content, social and PR, usually measured on reach or engagement.
A performance marketing agency narrows to channels that can be measured against cost:
Google and Microsoft: search, Shopping and Performance Max
Meta and TikTok: prospecting and retargeting for consumer brands
LinkedIn: B2B targeting by role and company
Amazon and retail media: for brands sold through marketplaces and retailers
Programmatic and CTV: reach and video at scale, measured with holdouts
Many London agencies offer both, so ask which metrics each retainer is judged on.
London Performance Marketing Agencies Compared by Channels, Measurement and Fit
Use the table to narrow by brand type and measurement depth. Fees are rarely published in London, so the entries note any pricing signals we found.
Agency | London base | Best fit | Channel strength | Measurement and CRO |
|---|---|---|---|---|
9AM | Remote (no London office) | Consumer, app and data brands; B2B | Google, Meta, TikTok, Amazon | Analytics and testing in-house |
WeDiscover | Southwark | Mid-size and enterprise brands | Paid search, paid social | Data collection, modelling, automation |
Croud | London HQ, plus Shrewsbury | Enterprise and international | Media, creative, data | Independent data team |
Brainlabs | London | Large brands, many sectors | Search, social, programmatic, retail media | Google Marketing Platform, data |
Jellyfish | The Shard | Global and multi-market brands | Full-funnel media, Google, Amazon, Meta | Data, cloud and AI tools |
Journey Further | London office, Leeds HQ | Consumer and finance brands | Search, social, programmatic | Marketing science |
Impression | Borough, Nottingham HQ | Mid-market brands | Paid media, SEO, digital PR | Analytics and CRO |
Vervaunt | City of London | Ecommerce and Shopify brands | Paid search, paid social | Ecommerce CRO and platform work |
Bark.London | London | Ecommerce businesses | Paid media and creative | Data-led creative testing |
ROAST | London | Brands needing paid and organic | Paid media, organic, GEO | Labs and data team |
Best Performance Marketing Agencies in London
The London performance marketing agencies below range from global groups to specialist ecommerce teams.
1. 9AM (remote team serving London brands)
Address: 90 Broad St, 2nd Floor, New York, NY 10004
9AM serves London brands from New York, planning paid media and creative around the footprint each London brand sells into: local boroughs, the whole UK or international markets. With 9AM, Yubo grew monthly sign-ups by 35% with local creators in Europe and North America, and NIQ cut CPA by 65% across 22 countries.
Its edge is creator-led creative tested against acquisition cost across markets. It reports on contribution margin, LTV:CAC and payback period, runs incrementality tests to separate true lift from sales that would have happened anyway, and calibrates media mix models to each client's P&L.
2. WeDiscover (Southwark)
Address: Flat Iron Building by Kitt, 44-46 Southwark St, London SE1 1UN
WeDiscover is a performance marketing agency in the Flat Iron Building on Southwark Street. Beyond paid search and paid social, it runs data collection, analysis and modelling, and automation as named services.
That data bench is the reason it ranks high here: measurement is staffed as its own practice. The agency also publishes thought leadership on agency selection.
3. Croud (London)
Address: The Bard Building, 20 Curtain Rd, London EC2A 3NG
Croud is an independent global media, creative and data agency headquartered in London, with offices in Shrewsbury, New York, Atlanta and Dubai. Its independence is a selling point for brands wary of holding-company media deals.
Campaign Global named it Independent Media Agency of the Year 2025. Its CroudOS platform and an on-demand network of 2,900+ specialists cover 118 markets. For camera marketplace MPB, it lifted ROAS 35% with first-party data, then helped the brand bring media in-house while revenue grew 25% year over year.
4. Brainlabs (London)
Address: Building 4, 2 Old Street Yard, London EC1Y 8AF
Brainlabs started in London and now runs paid search, paid social, programmatic and CTV, retail media and Google Marketing Platform work for large brands. It is ISO/IEC 27001 certified, which matters to enterprise security teams.
It is independent and founder-led, built for formal RFPs and audit requirements, and works across retail, financial services, travel, consumer tech, B2B SaaS and healthcare.
5. Jellyfish (The Shard)
Address: The Shard, 32 London Bridge St, London SE1 9SG
Jellyfish has been part of The Brandtech Group since 2023 and is based at The Shard. It combines media, creative, data and cloud with AI tools, and holds certifications across Google Marketing Platform, Google Cloud, Salesforce, Amazon and Meta, according to its company profile.
Its AI tools sit inside the media work: the Pencil platform, trained on $2.65 billion in ad spend, produces creative assets 55% faster, and Share of Model tracks how large language models describe a brand. One search strategy run across 38 markets delivered 19% growth on 14% less budget.
6. Journey Further (London)
Address: No London street address published (HQ: 4 The Dockside, Leeds)
Founded in 2017, Journey Further is a discovery-led performance agency with its HQ in Leeds and offices in London, Manchester and New York. It works across search, social, programmatic, creative and marketing science.
Recent wins include Workspace, the London flexible office group, for paid search, social, programmatic and data.
7. Impression (Borough)
Address: The Typewriter Building, 140 Borough High St, London SE1 1LB
Impression is headquartered in Nottingham and opened a London office in Borough in 2021. It runs paid media alongside SEO, digital PR and analytics, and won Biddable Team of the Year at the 2021 Drum Search Awards.
It markets itself as Performance Marketing Agency of the Year and runs accounts through a formal experimentation process built on its own tools. Its paid media work includes €6.5 million in revenue for an airline from Demand Gen campaigns and weather-triggered digital out-of-home ads for Norse Atlantic Airways. It is a certified B Corp.
8. Vervaunt (City of London)
Address: WeWork, 10 Devonshire Square, London EC2M 4YP
Vervaunt is an ecommerce agency based near Old Street and Devonshire Square. It pairs paid search and paid social with ecommerce platform and CRO work, which suits Shopify and DTC brands.
It is a small consultancy that also handles ecommerce replatforming, so ads and site changes come from one team. Clients include Sunspel, PANGAIA, The Frankie Shop and Timex, and for Osprey it localises paid search and social across France, Germany, Italy and the UK. It became a certified B Corp in July 2024.
9. Bark.London (London)
Address: Albert House, 256-260 Old St, London EC1V 9DD
Bark.London is a specialist performance agency that uses paid media, creative and data to grow ecommerce businesses. Creative production sits next to media buying, so new ads can be tested quickly.
It says it is the UK's only independent agency certified by Meta for strategy, creative and data, and it adds data science work such as attribution modelling and lifetime value analysis. Clients include Chilly's, hims and Lightyear.
10. ROAST (London)
Address: 1st Floor, 53 Frith Street, London, W1D 4SN
ROAST offers paid media, organic performance and GEO (visibility in AI search), with an R&D arm called ROAST Labs. It suits brands that want paid and organic search budgets balanced by one team.
Founded in 2015, it has offices in London, Cape Town, New York and Dubai and is a certified B Corp with a score of 91.1. Clients include Experian, AJ Bell, PitchBook and The National Lottery, and ROAST Labs builds tools that range from client scripts to full SaaS products.
PECR, UK GDPR and Consent Mode v2: Tracking Rules London Agencies Handle
Any London agency running paid media must set up tracking that complies with PECR and UK GDPR, and send Google the consent signals it needs. Weak consent setup either breaks measurement or exposes the brand to enforcement.
Cookie Consent Under PECR After the Data (Use and Access) Act 2025
New PECR rules came into force on 5 February 2026. They add consent exemptions for some low-risk cookies, such as certain analytics, but advertising and cross-site tracking still need consent, as Womble Bond Dickinson's summary of the ICO guidance explains. The ICO also reviewed cookie use on the UK's top 1,000 websites during 2025.
The Act raised PECR fines to UK GDPR levels, according to Kennedys' analysis, so a careless tag setup now carries real financial risk.
Google Consent Mode v2 and Modelled Conversions
Google's consent mode passes each user's consent choice to Google tags. When users decline, tags send cookieless pings and Google models the missing conversions. For UK and EEA traffic, consent signals are required to keep using audience and personalisation features.
Tracking Questions to Ask a London Agency
Which consent management platform do you support, and who maintains it?
Do you run consent mode in basic or advanced setup, and why?
What share of conversions is modelled, and how do you report it?
Do you use server-side tagging, and does it respect consent choices?
Agencies with a dedicated analytics practice should answer these without passing you to a third party.
How to Choose a London Performance Marketing Agency for Your Growth Stage
Match the agency to your stage: early brands need fast creative testing and clean tracking, scale-ups need incrementality testing and CRO, and enterprises need multi-market media, security standards and modelling. An agency that is excellent for one stage can be the wrong size for another.
Incrementality Testing and Media Mix Modelling
Platform-reported ROAS overstates impact when channels claim the same sale. Ask how the agency measures incremental lift:
Geo or audience holdouts for single channels
Platform lift studies on Meta and Google
Media mix modelling (MMM) once spend spreads across several channels
Google's open-source Meridian MMM has made modelling more accessible, but it still needs clean data and a team that can interpret it.
CRO and Landing Page Capability
More traffic to a weak page wastes budget. Prefer agencies that test landing pages and checkout flows, or that work closely with your web team on a shared test plan.
Warning Signs in London Agency Pitches
Results shown only as platform ROAS, with no holdout or blended view
A senior pitch team that will not run the account
No answer on consent setup or modelled conversions
Long notice periods with no performance review points
UK Brands Are Moving Budget Back Into Big Media
In Q3 2026, UK companies raised main media budgets at the fastest pace in nine years, a net balance of +9.8%, according to the IPA Bellwether. TV, outdoor and video are back on the plan.
When brand spend rises, every platform dashboard claims part of the result. Set up a holdout test before your next brand campaign launches, so you can see what search and social add on their own.
If you have never run a holdout test, book a strategy call with 9AM. We will help you design one before your next brand campaign goes live, so the 2027 budget is set on measured lift.
FAQs
How much does a performance marketing agency in London cost?
The price varies widely from £1,200 to £17,000+ per month. Most agencies charge a monthly retainer in GBP based on scope, sometimes plus a share of media spend or a performance bonus. Few publish prices, so request a written scope with fees at your current and planned spend.
Do I need an agency with a London office?
Only if in-person workshops or UK-specific retail and media relationships matter to you. Many London brands work with teams based elsewhere in the UK or abroad, provided the agency handles UK consent rules and reporting.
Which London agencies suit ecommerce brands?
On this list, Vervaunt and Bark.London focus on ecommerce, and 9AM, Brainlabs and Jellyfish run Amazon and retail media alongside paid search and social.
About Mustafa Alkhtab
Mustafa Alkhtab is Head of Performance Media at inBeat, where he oversees paid media and performance creative results across the agency's accounts. Before inBeat, he built growth programs for ecommerce, lead generation, and mobile app businesses in international markets. He writes about media buying, measurement, and conversion rate optimization.
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