How are you going to avoid the problems which other Bitcoin services have encountered with UK banks?
i have found a solution to this because, while alpha testing my service I found out that an actual UK bank account transfer is slow where some banks do not instantly deposit funds. I do have a more detailed explanation of how I got around this but I dont want to make it public for others to compete. Any serious investor can PM me the plan as long as it doesnt show the entirety of the plan on public forums for people to steal my idea. Lets just hint at the use of a prepaid card that fresh customer top up my master account (shows instantly). I thank god for this as it solves your banking question and helps me get closer to my next phase I had planned in one swoop, Withdrawals via prepaid cards.
I'm more interested in why you think that your service won't encounter the same AML/KYC compliance problems with the banks which other services have had to deal with, resulting in the sudden freezing/shut-down of their bank accounts - something which would be absolutely catastrophic to your service given the business model you've outlined.
You've also said nothing which addresses the issue of whether you'd be regarded as operating a financial service or selling a financial product under UK law. Potential investors are going to want more than just your assurances on this - it's totally reasonable for them to require a written legal opinion setting out
why your service will be exempt from regulation.
Also, potential investors are going to be less interested in best case scenarios (this mythical land in which you have no significant over-heads and nobody ever rips you off and your bank doesn't slam you with KYC/AML issues) than they are in worst case scenarios.