Is there a sex work project near you?
Also, is it worth making a regular GP appointment to ask about this? Or perhaps asking at your GUM clinic? I know a GP won't necessarily know but they may well at least have ideas, and my GUM clinic certainly do seem to know all about every available service in the vicinity to help anyone who's ever even thought about sex and/or sex work in any way. They are in Soho, though!
I want to send some hugs your way, too, mia - I hope you feel better soon. And I know this is a lot easier to say than to act upon, but really, people who work for the NHS are usually very far from judgemental. You should feel safe asking about specific services available; you needn't tell them any personal details if you don't wish to, and they shouldn't ask.
Perhaps even that
NHS Direct phoneline could be of use? It's certainly anonymous and I assume they'd have information that they could pass on about different sorts of counselling services available in your area?
The main thing, I think, is to make someone aware of what you need, even your doctor if you would feel comfortable at least giving them an outline of your situation. Then they can start doing referrals for you and making sure you are seen by the right person. Remember, you're in no way obliged to take up any of their suggestions - it's not like they can have you locked up or stuck in intensive therapy or anything!
You're the one who can choose whether or not to take any advice given, and you're completely entitled to ask about anything you need.
((Hugs))