Internal Knowledge Assistant with RAG for a Consulting Firm: Cost in London (2026)

The verdict in three sentences

In a consulting firm, value sleeps in past deliverables: methods, benchmarks, winning proposals that nobody can find under the pressure of a tender. A custom RAG assistant at GBP 22,000 to 43,000, hosted in the UK or EU and enforcing per-client folder access rights, answers in seconds with cited sources. With 2 hours saved per consultant per week and usage costs of GBP 260 to 1,050 per month, the project pays back within a quarter.

Generic copilot, SaaS tool or custom RAG

A partner at a London strategy consulting firm (80 consultants) holds 12,000 archived deliverables on SharePoint: decks, scoping notes, financial models. Junior consultants spend an average of 3 hours a week looking for a reference or asking a manager who "remembers a similar engagement".

2026 ballpark: over 3 years, a tool at GBP 35 per user costs about GBP 100,800, versus GBP 31,000 to 81,000 for a custom RAG that the firm owns.

Architecture and UK GDPR compliance

RAG (retrieval-augmented generation) splits documents into passages, indexes them in a vector database and feeds the language model only the extracts that are relevant and authorised for the user asking the question.

Under UK GDPR, the firm remains the data controller: a DPIA if client personal data appears in deliverables, a processor agreement with each supplier, and limited retention of queries (90 days is common). Deliverables under strict confidentiality clauses can be excluded from the index.

Mini case study

Charlotte, partner at an 80-consultant firm in London, takes a cautious assumption: 2 hours saved per consultant per week, over 44 working weeks, or 7,040 hours a year. She only values half of it, since the rest dilutes into other tasks: 3,520 hours at a loaded internal cost of GBP 60, or GBP 211,200 a year of freed capacity.

The project costs GBP 35,000 plus GBP 700 per month. Even if only 10% of that capacity turns into billable hours or better-prepared proposals, or GBP 21,120 a year, the first-year cost (GBP 43,400) is covered in just over 2 years. With a third of the capacity converted, payback drops under 8 months.

FAQ

How much does a RAG assistant cost for a consulting firm in 2026?

Plan GBP 22,000 to 43,000 of setup depending on document volume and number of sources, then GBP 260 to 1,050 per month for hosting and model calls.

Is the firm's data used to train the model?

No, as long as the API provider contract excludes it, which is standard for business offers in 2026. Documents stay in your vector database hosted in the UK or EU.

How do we stop a consultant seeing a competing client's documents?

The assistant applies the source system's access rights, folder by folder. A consultant never receives an extract from a folder they could not open in SharePoint.

How long does deployment take?

About 10 weeks: 2 for scoping and taxonomy, 5 for building and indexing, 3 for a pilot with 10 to 15 consultants before firm-wide rollout.

Can the answers be wrong?

The risk exists, hence sources are always shown with a link to the document. A set of 100 test questions measures accuracy before going live.

Let's scope your project. Tell us your deliverable volume and your Microsoft or Google environment and we will price a RAG assistant between GBP 22,000 and 43,000, delivered in 10 weeks. Detailed quote within 48 h. WhatsApp +221 77 596 93 33.