SaaS Marketing: Consultant or Agency in London?

I see this question come up a lot with London SaaS founders, and frankly, most of the advice out there is rubbish. People frame it as a simple choice between two service models, but that’s the wrong way to look at it. You’re not just choosing between a solo expert and a team; you’re choosing a partner to solve a very specific business problem at a specific stage of your company's life.

Getting it wrong means burning through your seed funding with nothing to show for it but a fancy dashboard and a list of excuses. Get it right, and you find a partner that plugs directly into your growth engine and helps you hit your next milestone. I've been on both sides of the table, running campaigns and advising founders, and the difference between success and failure often comes down to making the right choice here before a single penny is spent on ads.

So, let's cut through the noise. This isn't about which is "better." It's about which is right for *you*, right now.

So, what's the actual difference?

Forget the sales pitches for a second. At their core, consultants and agencies are built to do different things. Understanding this is the first step.

A SaaS Marketing Consultant is a strategist. You're hiring a specific person for their brain and their experiance. Their job is to diagnose complex problems, create a strategic roadmap, and often, to train your team to execute it. They are the architect who draws up the blueprints. They're best for answering the "what" and "why." Why isn't our funnel converting? What channel should we focus on first? What's the right message for our ICP?

They usually work on a retainer or project basis, embedding themselves in your business for a period to solve a specific challenge. It’s a high-touch, deeply involved relationship. Think of them as a fractional, senior-level marketing hire without the full-time salary and equity package. They help you figure out the game.

A SaaS Marketing Agency, on the other hand, is an execution engine. You're hiring a system, a process, and a team of specialists (ad managers, copywriters, designers, analysts). Their job is to take a validated strategy and scale it efficiently. They are the construction crew that builds the house according to the architect's blueprints. They're best for the "how" and "how much." How do we get this campaign live on three platforms by next week? How much can we scale the budget while maintaining our target CPA?

Agencies are brilliant when you have product-market fit and a clear idea of what works. They bring the manpower and processes to do the work at a scale and speed that's impossible for a small in-house team. They help you win the game you're already playing.

The mistake founders make is hiring a construction crew to design the building, or an architect to lay the bricks. Both scenarios end in frustration and wasted money.

When should a London SaaS founder hire a consultant?

Hiring a consultant makes sense when you're facing uncertainty and need high-level strategic thinking more than you need raw manpower. Here are a few common scenarios where a consultant is almost definately the right choice:

1. You're Pre-Product-Market Fit (or just found it).
You have a product, maybe some initial traction, but you haven't yet nailed your Ideal Customer Profile (ICP), your core messaging, or your primary acquisition channel. Spending big with an agency at this stage is like pouring petrol on a fire that hasn't been lit yet. A consultant will work with you to test hypotheses, interview customers, and find that initial, repeatable go-to-market motion. This is about discovery, not scale.

2. Your Unit Economics Are Broken.
You're getting signups, but your Customer Acquisition Cost (CAC) is higher than your Lifetime Value (LTV), or your payback period is terrifyingly long. An agency might be able to get you cheaper clicks, but a consultant will diagnose the root cause. Is it a pricing problem? A churn problem? An activation problem? They'll look at the entire funnel, from ad to retained customer, and rebuild your growth model so it's actually profitable. Getting this right is fundamental before you even think about scaling, a topic we explore in our London tech founder's guide to B2B paid ads ROI.

3. You Have an In-House Team That's Hit a Plateau.
You might have a couple of junior marketers running campaigns, but you've hit a ceiling. Results have flatlined, and they lack the senior experience to know what to do next. A consultant can act as a player-coach, bringing in senior expertise to guide your team, implement new frameworks, and upskill them in the proccess. It's a great way to invest in your people while also solving a critical growth problem.

4. You Need to Solve a Very Specific, Niche Problem.
Maybe you need to crack LinkedIn Ads for a highly specific enterprise audience, or build out a complex B2B retargeting strategy. Generalist agencies often struggle here. A specialist consultant who has deep, proven experience in that one specific area can come in, solve that one problem, and then leave. It's surgical, effective, and cost-efficient.

For many SaaS businesses in London, especially those coming out of incubators around Shoreditch or Level39, a good consultant is the bridge from a raw product to a scalable business.

So when does an agency make sense?

Don't get me wrong, a great agency can be a massive accelerant for your growth. But they work best when you can hand them a validated playbook and say "go." Here’s when to pull the trigger on an agency:

1. You Have a Proven, Repeatable Funnel.
You know exactly who your customer is, what message resonates with them, and which one or two channels reliably produce customers at a profitable CAC. You're not guessing anymore. Your problem has shifted from "what works?" to "how do we do more of what works, faster?".

2. You Need to Scale Execution, Fast.
You're at a point where the sheer volume of work is the bottleneck. You need to be testing dozens of ad creatives, writing new landing page copy, managing campaigns across multiple platforms, and analysing the data. This is what agencies are built for. They have the teams and systems to manage this complexity and volume in a way a founder or small team simply can't. I remember one campaign we worked on for a B2B software client where we generated 4,622 registrations at just $2.38 each, because we could scale the execution of a working formula.

3. You Need a Breadth of Skills You Can't Hire In-House.
To run paid acquisition properly, you need an ad strategist, a copywriter, a designer, and maybe a data analyst. Hiring all those roles full-time in London is incredibly expensive. An agency gives you access to that entire team for a single monthly fee. For a growth-stage startup, it's a much more capital-efficient way to get the skills you need.

4. You Want Predictability and Systems.
Good agencies run on process. They have established workflows for onboarding, reporting, creative testing, and optimisation. This can bring a level of discipline and predictability to your marketing efforts that can be hard to build from scratch. When you're reporting to a board and need to forecast your growth, this systematic approach is invaluable. If you find yourself in this position, our ultimate guide to vetting a B2B tech ad agency in the UK can be a lifesaver.

A Visual Guide: Making The Right Choice

Sometimes a simple flowchart can cut through the complexity. I've put together a quick visual guide to help you think through this decision based on your current business stage. Follow the path that best describes your situation.

Cost vs Value: What to Expect in the London Market

Let's talk about money. This is often the deciding factor, but it shouldn't be. Choosing the cheaper option is almost always the more expensive mistake in the long run. The London market is competitive, and prices can vary wildly, but here's a realistic breakdown of what you should expect to invest.

SaaS Consultants in London:
You're paying for senior-level expertise, so expect to pay a premium. Most experienced consultants will charge either a day rate or a monthly retainer.

• -> Day rates: £800 - £2,000+ per day, depending on their experience and track record.
• -> Monthly retainers: £4,000 - £10,000+ per month. This usually covers a set number of days or a specific scope of work focused on strategy, oversight, and workshops.

SaaS Agencies in London:
Agency fees are typically structured as a monthly management fee, often with a percentage of ad spend component as you scale.

• -> Monthly retainers: £3,000 - £15,000+ per month. For early-stage startups, you're likely in the £3k-£6k range. This fee covers the team's time for management, reporting, and basic creative.
• -> Percentage of Ad Spend: 10-20%. This often kicks in above a certain spend threshold (e.g., £20k/month).
• -> Setup Fees: Some agencies charge a one-off fee of £2,000 - £5,000 for initial setup and strategy.

It's vital to understand what's included. Does the agency fee include copywriting and design, or is that extra? How much access do you get to the senior strategist vs. a junior account manager? These are critical questions to ask, and you can find more details in this 2024 guide on UK paid ads management costs.

But the raw cost is meaningless without context. The real question is: what CAC can you afford? This comes down to your LTV. If you don't know this number, stop everything and calculate it now. It's the most important metric in your business.

The Vetting Proccess: How to Spot the Real Deal

Whether you choose a consultant or an agency, you need to know how to separate the experts from the pretenders. The London market is saturated, and many talk a good game. Your job is to pressure-test their claims. Don't just look at their case studies; dig into their thinking.

Questions to ask a potential CONSULTANT:

• -> "Walk me through your diagnostic process. If you started with us on Monday, what would you do in the first 30 days?" (Look for a structured approach, not vague promises).
• -> "Tell me about a time you advised a SaaS client to STOP spending on a channel. Why?" (This tests for honesty and strategic thinking over just spending budget).
• -> "Based on what you know about our business, what's a core assumption you'd want to challenge first?" (Good consultants are professional sceptics).
• -> "What's a contrarian view you hold about B2B SaaS marketing that most people get wrong?" (You want an original thinker, not someone who just regurgitates blog posts).

Questions to ask a potential AGENCY:

• -> "Can you show me a case study for a UK-based B2B SaaS with a similar annual contract value to ours?" (Get specific. Generic B2C e-commerce results are irrelevant).
• -> "Who, specifically, will be working on our account day-to-day? Can we meet them? What is their direct experience with paid ads for SaaS?" (Don't get sold by the founder and handed off to a junior).
• -> "What is your process for ad creative and copy iteration? How quickly can you test new angles?" (You need an agency built for speed and testing, not one that delivers 3 ad variants a month).
• -> "How do you report on performance beyond just platform metrics like CTR and CPC? Show me a sample report." (Look for a focus on business metrics: pipeline, SQLs, revenue, and LTV:CAC).

This vetting stage is critical. To help you navigate it, we've compiled a more detailed framework in our ultimate guide to vetting paid ad agencies in London. Don't sign a contract until you're completely confident in their expertise and approach.

My final recommendations for you

This has been a lot to take in, so let's simplify it. I've broken down the key decision factors into a table to give you a clear, side-by-side comparison. Use this as your final checklist before making a decision.

Ultimately, the choice between a consultant and an agency is a reflection of your company's maturity. Be brutally honest with yourself about what your biggest problem is right now. Is it a lack of a clear plan, or a lack of hands to execute the plan you already have? Once you have that answer, your decision becomes much, much easier.

Navigating this landscape, especially in a competitive hub like London, can be daunting. The right partner can be the difference between stagnation and explosive growth. If you're still unsure or want to discuss your specific situation, many consultancies and agencies (including us) offer a free initial consultation or strategy session. It's a no-risk way to get an expert opinion on your challenges and see if there's a potential fit. Taking the time to find the right partner is one of the highest-leverage decisions you can make as a founder.