UK Startup's Guide: Vetting Paid Ad Agencies

Choosing a paid ad agency as a UK startup is a complete nightmare. I get it. You're bombarded with jargon, flashy promises, and case studies from massive brands that have nothing to do with your reality. Most founders end up either paralysed by choice or, worse, signing a 12-month contract with a slick agency in London that assigns their account to a junior exec who's just learned what "CPC" means. It's a quick way to burn through your seed funding.

The fundamental problem is a massive mismatch. Most agencies are structured to serve established businesses with £50k+ monthly ad spends. Their processes are slow, their retainers are bloated, and they care more about winning awards than hitting your MRR targets. They don't understand the urgency and the need for profitable, scrappy growth that defines a startup. You don't need a massive team; you need a single, sharp expert who lives and breathes this stuff and can act as an extension of your own team.

So, why is finding a genuinely good agency so bloody hard?

It's because you're probably looking for the wrong things. A cool office in Shoreditch, a big team, or a client list that includes a FTSE 100 company are vanity metrics. They mean nothing for your B2B SaaS or D2C eCommerce startup. These agencies are built on a model of leverage – senior people sell, junior people do the work. For a startup, that model is a death sentence. You're paying a premium for the senior partner's expertise, but your account is actually being managed by someone learning on your dime.

You need a partner who understands that an extra £5 CPA could be the difference between hitting payroll and not. You need someone who gets excited about split-testing landing page copy at 11 PM, not someone who needs a week to get a report approved by three layers of management. The truth is, the best 'agencies' for startups often aren't big agencies at all. They are small, specialist consultancies or even solo experts who are deep in the trenches, running campaigns day-in, day-out. Forget the big agency search; what you really need is to find an expert you can trust. This is where a proper vetting process for any paid ad agencies you're considering becomes absolutely critical.

What should I actually be looking for then?

Alright, let's cut through the noise. Here’s what actually matters when you're assessing a potential partner. It's not complicated, but it requires you to ignore the sales pitch and focus on the evidence.

1. Case Studies That Actually Mean Something

Don't just glance at the headline ROAS number. Dig in. Are the case studies for businesses like yours? If you're a B2B SaaS founder, a case study about a fashion brand's 10x ROAS is completely irrelevant. The audiences, sales cycles, and strategies are worlds apart. I've run campaigns for software companies where we've achieved things like 5,082 software trials at $7 a pop. That's a specific, meaningful result for a SaaS business. Another time, we took a medical job matching platform from a £100 CPA down to just £7. That's the kind of tangible, needle-moving result you should be looking for. If they can't show you specific results for a company that looks and feels like yours, they probably can't get them for you either.

2. The Free Consultation Test

Any decent consultant or agency should offer a free initial chat or strategy session. This is your single best opportunity to vet their expertise. Don't let it be a one-way sales pitch. Come prepared with your toughest questions. Ask them what they think of your current strategy. Ask them what audiences they'd test first. Ask them what quick wins they see.

You should walk away from that call with at least 2-3 actionable ideas you could implement yourself, for free. If you leave the call feeling like you've just been given a hard sell and learned nothing, they failed the test. When we do these calls, we literally open up a client's ad account with them on screen and start pointing out opportunities. It gives them immediate value and proves we know what we're talking about. If a potential partner isn't willing to do that, they're either not confident enough in their skills or they're hiding something.

3. Brutal Honesty Over Unrealistic Promises

If an agency "guarantees" you a certain ROAS or number of leads, run. Run fast and don't look back. Paid advertising is not a magic box. It's a process of rigorous testing, data analysis, and iteration. No one can predict exactly how a campaign will perform. A true expert will be honest about this. They'll talk about benchmarks, initial testing phases, and a methodical approach to finding what works. They'll be transparent about the risks and the potential rewards. I'd much rather hire someone who tells me "Look, the first month is going to be about data collection and we might not be profitable, but here's our plan to get there" than someone who promises me the moon on a stick.

4. Who is Actually Doing the Work?

This is a big one. You need to ask, point blank: "Who, specifically, will be building and managing my campaigns?" If the answer is vague or they talk about "our team of experts," it's a red flag. You want to be speaking directly with the person whose hands will be on the keyboard. For a startup, direct access to the senior strategist is non-negotiable. You don't have time for your feedback to be passed through three layers of account managers. This is why many founders find that working with specialist paid ad consultants can often be a better fit than a larger agency structure.

How do I know if they *really* get startups?

This is the crux of it. An agency can be technically brilliant at running Google Ads but still be a terrible fit for a startup if they don't understand the mindset. Here's how to tell the difference.

They should be obsessed with your business metrics, not their ad metrics. A good startup-focused agency cares less about CTR and more about your LTV:CAC ratio. They should be asking you about your churn rate, your average revenue per user, and your sales conversion rates. Why? Because without this information, it's impossible to know how much you can actually afford to spend to acquire a customer. They need to understand that a "lead" is worthless unless it turns into a paying customer that sticks around.

This is so important that I insist new clients work through these numbers with me before we even think about ad spend. You cannot run profitable ads in a vacuum. You need to know the fundamental economics of your business.

To help with this, I've built a simple calculator below. Play around with it. Figure out your LTV and what a healthy Customer Acquisition Cost (CAC) looks like for you. Armed with this number, you'll go into conversations with agencies from a position of power.

What are the red flags I should absolutely run from?

Okay, let's talk about the deal-breakers. If you see any of these, it's a hard pass. Your time and money are too valuable to waste.

• Long-Term Contracts: A 12-month contract for an early-stage startup is insane. You have no idea what your business will look like in 12 months. A good partner will be confident enough in their results to work on a rolling monthly basis after a short initial period (e.g., 3 months). They should have to earn your business every single month.
• The "Proprietary Software" or "Secret Sauce" Pitch: This is almost always rubbish. Success in paid ads comes from solid strategy, relentless testing, great creative, and a deep understanding of the platform's algorithm. It's not magic. If they can't explain their process in simple terms, they're likely hiding a lack of a real strategy.
• Percentage of Ad Spend Fees: This is a common model, but it's often a bad fit for startups. It creates a conflict of interest where the agency is incentivised to make you spend more, not necessarily more profitably. A flat monthly retainer is much better as it's predictable and ensures they are focused on getting you the best results for your budget. The decision of whether to bring someone in-house or hire an agency often comes down to these cost structures.
• The Bait-and-Switch: This is the oldest trick in the book. You have a brilliant sales call with a seasoned, impressive director. You sign on the dotted line, and then you're handed off to a junior account manager who you've never met. You must insist that the person you vetted and built rapport with is the person managing your account day-to-day.
• Asking for References Late in the Game: This might sound contrarian, but from my side of the table, if a potential client has seen our detailed case studies, had a deep-dive strategy call with us, and seen our reviews, and *then* asks to speak to one of our current clients, it's a bit of a red flag for us. It signals a fundamental lack of trust that probably won't lead to a good partnership. A good agency should have provided enough proof upfront that a reference call isn't necessary.

To make this a bit easier to visualise, here's a simple flowchart for your vetting process.

How much should I actually expect to pay an agency in the UK?

This is the million-dollar—or, rather, thousand-pound—question. The answer varies, but for a startup, you need predictability. As mentioned, the percentage of ad spend model is risky. The performance-based model sounds great, but it's rare to find and often comes with complex terms. That's why I almost always recomend a flat monthly retainer for startups. You know exactly what you'll pay each month, making it easy to budget your cash flow. This is a topic we've covered in detail in our guide to paid ads management costs in the UK.

For a good, specialist consultant or small agency in the UK focused on startups, you should expect to pay a monthly retainer somewhere between £1,500 and £4,000 per month. Anything less than that, and you're likely getting someone very inexperienced. Anything significantly more, and they probably aren't geared towards serving early-stage companies. This fee is for their management, strategy, and expertise; your ad spend is a separate budget on top of this.

Here’s a quick visual breakdown of the common pricing models and how suitable they are for a typical startup.

Ultimately, finding the right partner comes down to a simple question: do you trust this person or team to be a good steward of your limited capital? Your goal shouldn't be to just hire any ad expert, but to find a partner who will care about your growth as much as you do. They should feel like a part of your team, not just another vendor on your expense report.

So, what's the final verdict?

Stop searching for "the best paid ad agency in the UK." Instead, start searching for "the right paid ad expert for my startup." It's a subtle but powerful shift in mindset. It moves you away from being impressed by big names and towards valuing specific, relevant expertise and a true partnership approach.

Do your homework. Use the frameworks I've laid out here. Trust your gut. A good partnership is built on trust, transparency, and a shared obsession with results. Don't settle for anything less. Your startup's future could depend on it.

I've summarised the main points in a checklist for you below. Use it as a guide during your search.

Making the right choice of agency or consultant is one of the most impactful decisions you can make in the early stages of your company. Getting it right can pour fuel on the fire of your growth; getting it wrong can be a costly, time-consuming distraction you just can't afford.

If you've read through this and feel like you need an expert partner who thinks like a founder and is focused on profitable growth from day one, you might be the kind of startup we love to work with. We offer a completely free, no-obligation strategy session where we'll dive into your business and your ad accounts and give you our honest assessment and actionable advice. If we're a good fit, we can discuss what a partnership looks like. If not, you'll still walk away with a ton of value. Feel free to get in touch to schedule your free consultation.