From what I can see, Strata Consultants offer a comparison service to allow you to choose your new manager and will assist with the transfer of the business from your current manager to your new one.
What I sense you are looking for is a company that will help you to divest yourself of a manager in mid-contract. I’m not sure that they will do that (but they might – ask!).
They may be able to advise you on the conditions that will allow you to break your contract – i.e. the terms of your contract that might have been breached – but I can’t see how they can do more than that.
What it comes down to is examining your contract, establishing the terms under which you can terminate and then work from there.