I wish you all the luck in the world with this, ClareBear! I'm in the US myself, and can't even find a laboratory that tests for silicone. I'd be more than happy to pay for it myself (do you even have that option over in the UK?), if I could just find out where to have the test done. I'm sorry I can't be of any help to you (other than moral support).
I do wish we could get all of us who are suffering with these horrible symptoms together in a room with all the doctors who poo-poo our symptoms and try to tell us they're all in our heads. If we could show them our sheer numbers and get them to listen to the same story over and over from thousands of different women, maybe they'd realize we can't all be crazy.