Do you necessarily need to the provider to be physically based in the UK or simply service coverage is enough?
Leadvue Technologies specializes in building DLP, encryption technologies in-sync with the Policy, Strategy, Business's Risk Apetite & Tolerance. This includes effective GAP analysis between the current & future states.
For Discovery, Classification, Mitigation and Remediation we can use the Symantec's DLP Solution, unless you have something else in mind or if you need to perform a vendor selection using a precise vendor selection matrix. For classification, we could explore something in the range of Titus Classification suite or even Symantec's data insight.
Let me know if this sounds interesting to you. I'd be glad to setup a call to discuss this further.