Can you advise a UK questioner?

I suspect the answer is no, as this seems to be an American based forum.  I am British and being treated under the NHS, and to be honest, recently have had some expensive investigations so cannot complain too much.  The fact is though that it has not always run so smoothly, and I have had to wait a very long time to get investigations and/or treatments which are not always fully what I need, so slowing up the diagnostic and treatment process.  I have often wished to go private.  The problem is no insurance company will touch me because I have pre-existing conditions, and am clearly going to cost them a lot of money in the long term.  Do you know if there is any way around this?  Right now the NHS is offering me a top class service, but this is after over a decade of being left in the wilderness, and I could be thrown back onto the scrapheap at any time.  Do you know anything about UK services?  To complicate things I have been on long term disability unable to work and am very poor, getting daily poorer.  I am still fighting to get disability allowance, they make it almost impossible here, unless you can prove you have less than six months to live, seriously.  Any help or advice?  Thanks.