London's Guide To Vetting Paid Media Agencies

Finding a decent paid media agency in London feels like a nightmare, doesn't it? The city is crawling with them. You've got the big network agencies in Soho with shiny foyers, the boutique shops in Shoreditch that talk a good game about 'growth hacking', and countless one-man-bands promising the earth. Most founders I speak to get burned. They sign a 6-month contract based on a slick presentation and end up with vanity metrics, a lighter bank account, and zero actual growth.

The problem is, you're asking the wrong questions and looking for the wrong things. You're being sold to, when you should be conducting an audit. You need to stop evaluating agencies and start evaluating potential growth partners. The difference is massive. A vendor executes tasks; a partner challenges your assumptions and holds you accountable to the numbers that actually matter. This guide is about how to find the latter. It's a framework we've developed from seeing hundreds of businesses, both in London and globally, make the same costly mistakes.

So, you think you're ready to hire an agency?

Before you even think about Googling "PPC Agency London", you need to get your own house in order. An agency is an amplifier. If you give them a broken business model or a fuzzy understanding of your customer, all they'll do is amplify your losses, faster. A proper agency will force you to answer these questions anyway, so you might as well get ahead.

Your first job isn't to write a brief. It's to become a stone-cold expert on the economics of your own business. It's shocking how many founders can't answer the most basic questions about their own unit economics. If you go into a discovery call without this knowledge, you are practically begging to be taken for a ride. A sharp agency will spot it a mile off. If you want to make sure you're doing this right, it's worth reading up on how to properly vet an agency for actual ROI, not just clicks and impressions.

The absolute starting point is figuring out what a customer is actually worth to you. Without this number, every conversation about Cost Per Lead or ROAS is meaningless. This is where you must calculate your Customer Lifetime Value (LTV). It's not optional.

Once you have this number, everything changes. A £300 lead from a Google Ad doesn't look expensive if you know the LTV of that customer is £15,000. It looks like a bargain. This single calculation frees you from chasing cheap, low-quality leads and allows you to build a sustainable, scalable customer acquisition machine. It is the fundamental metric to fixing your paid ads ROI.

Are you selling a solution or just a product?

The second piece of homework is to get brutally honest about your offer. I've seen countless campaigns fail not because the ads were bad, but because the offer was weak, confusing, or irrelevant. The number one reason campaigns fail is a lack of demand for the offer.

You need to stop thinking in terms of features and start thinking in terms of pain. Your Ideal Customer Profile (ICP) isn't a demographic; it's a nightmare. The Head of Sales at a tech firm near Old Street isn't buying "CRM software." She's buying a solution to her nightmare: her best reps leaving because they're buried in admin, while she's getting grilled by the board about a weak pipeline. Your ad and your landing page must speak directly to that nightmare.

A great offer does three things:

1. It targets a specific audience. Not "SMEs", but "UK-based SaaS companies with 50-200 staff who have just raised a Series A". The more specific, the better.
2. It solves an urgent, expensive problem. Not "we improve efficiency", but "we stop you losing your best engineers because of a clunky development workflow".
3. It's packaged clearly. A productised service with a clear name, defined deliverables, and a timeline is far easier to sell than a vague "consulting" offer. It reduces the perceived risk for the buyer.

If your offer is weak, no amount of ad spend will save it. A good agency will tell you this. A bad one will take your money and blame the algorithm when it fails.

The Vetting Framework: How to Separate the Experts from the Pretenders

Right, you've done your homework. You know your LTV, you know your CAC target, and you're confident in your offer. Now you can start talking to agencies. This isn't a chemistry test; it's a cross-examination. Your job is to extract proof of expertise, not to be wowed by a deck.

When you're looking for London ad experts that get real results, your entire focus should be on their past work. Forget their awards, their blog posts, their fancy office. The only thing that matters is a track record of solving similar problems for similar businesses.

Drill into their Case Studies

This is where the audition really begins. Don't just accept a PDF with a few client logos. You need to dissect their case studies like a detective.

• -> Relevance: Have they worked with B2B SaaS companies before? Or high-end eCommerce? Experience in your specific sector is a huge advantage. They'll understand the benchmarks, the sales cycles, and the language of your customers. For example, we've worked with a medical job matching SaaS where we reduced their CPA from £100 down to just £7. That kind of specific experience is gold dust.
• -> Recency: Are their success stories from last quarter or from 2018? The ad platforms change constantly. What worked two years ago might be irrelevant today.
• -> Real Numbers: Vague claims like "we boosted engagement" are worthless. You need hard metrics. Look for CPL (Cost Per Lead), CPA (Cost Per Acquisition), ROAS (Return On Ad Spend), and revenue figures in pounds. A great case study will say something like, "We generated £107k in revenue at 618% ROAS for a prize draw client." That's a real result.
• -> The 'Why': A good case study doesn't just show the results; it explains the strategy. Why did they choose LinkedIn over Meta? What targeting did they test? What was the thinking behind the ad creative? This shows they have a repeatable process, not just dumb luck.

If an agency is cagey about sharing detailed case studies, that's a massive red flag. It usually means they don't have them.

The Discovery Call is Their Audition, Not Yours

This is your chance to turn the tables. Most founders go into these calls ready to give their life story. Don't. You should be the one asking the probing questions. A good agency will love this; it shows you're serious. A weak one will get flustered.

Your goal is to see if they can think strategically about *your* business. A free consultation or account review should feel incredibly valuable. You should walk away with at least two or three actionable ideas you could implement yourself. We offer this to all potential clients, and it's where we prove our expertise before a contract is ever mentioned. It builds trust. Tbh, if someone asks us for client references *after* we've given them a free, in-depth strategy audit and shown them detailed case studies, we know it's not a good fit. It signals a fundamental lack of trust that will poison the relationship from day one.

Here are some killer questions to ask:

• "Based on my LTV and target CAC, which platform would you start with and why?"
• "What's the biggest mistake you see companies like mine making with their paid ads?"
• "Can you walk me through a campaign you ran for a similar client that *didn't* work at first, and how you turned it around?"
• "Who exactly will be working on my account? Can I speak with them?"
• "What does your reporting look like, and how often will we meet?"

Their answers will tell you everything you need to know about their depth of expertise and their process.

London Agency Pricing: What to Expect and What's Fair

Cost is obviously a huge factor, and pricing structures can be confusing. The cheapest option is almost never the best. You're paying for expertise and time, and good people cost money, especially in London. Debating whether to hire an agency or build an in-house team often comes down to this very point. Here's a breakdown of the common models and what you might expect to pay.

For most businesses spending under £20k/month on ads, a flat retainer is often the most transparent and effective model. It allows the agency to focus purely on getting you the best results for your budget without being incentivised to simply crank up the spend. As you scale, a hybrid model can be a great way to ensure everyone is pulling in the same direction. For a deeper analysis, you can check out this founder's guide to London ad agency pricing.

The First 90 Days: Setting the Foundation for Success

Signing the contract is not the finish line; it's the start of the race. The first three months of working with a new agency are absolutely critical. This is where the foundation for long-term growth is laid. If an agency promises you instant results in week one, they're either lying or incompetent. Real, sustainable growth takes a methodical approach.

Month 1: Audit, Setup & Data Gathering. The first 30 days should be all about deep learning and technical setup. They should be auditing your existing accounts, installing tracking pixels perfectly, defining conversion events, and getting a deep understanding of your customer. They'll likely launch initial test campaigns with a variety of audiences and creative angles. The goal here isn't massive ROAS; it's to gather clean data and learn what resonates and what doesn't. You should expect lots of communication and questions during this phase.

Month 2: Optimisation & Iteration. Armed with data from the first month, the agency should now start making intelligent decisions. This means turning off losing ads and audiences, and reallocating budget to the early winners. They should be split-testing ad copy, headlines, and landing page variations to improve key metrics like CTR (Click-Through Rate) and CVR (Conversion Rate). You should start to see some positive momentum and a clear path forward.

Month 3: Scaling What Works. By the end of the second month, you should have a few proven campaigns that are delivering a consistent return. Month three is about carefully scaling these winners. This doesn't just mean increasing the budget. It involves expanding lookalike audiences, finding new pockets of interest targeting, and introducing new creative that builds on what you've learned. By the end of the first 90 days, you should have a predictable system for acquiring customers that you can confidently invest more into.

This entire process requires trust and patience. Advertising is a process of systematic testing, not a magic bullet. The right paid ads agency partner will be transparent about this process from day one.

This is the main advice I have for you:

Choosing the right agency in a crowded market like London is tough, but it's not impossible if you follow a structured process. Here's a final checklist to guide your decision.

Ultimately, hiring an agency is a significant investment. It's not just the fee; it's the ad spend and the opportunity cost of getting it wrong. By approaching the process with rigor, focusing on proven expertise over slick salesmanship, and treating it as a search for a strategic partner, you drastically improve your chances of finding an agency that will actually deliver the measurable results and strong ROI you're looking for.

If you're a London-based founder who has done their homework and is ready to have a serious conversation about growth, you might benefit from some expert help. We offer a free, no-obligation 20-minute strategy session where we'll audit your current efforts and provide you with an actionable plan. It's a chance to see how we think and decide if we're the right partner to help you scale.