UK: Have you used private healthcare i.e. BUPA?

I have a serious question & would like answers from people in the UK only who've used BUPA or other private healthcare to resolve an arthritic, or rheumatoid problem, because their NHS GP &/or NHS hospital were useless. I'd like to know whether your experience was good & most of all how you arranged for your private consultation & the procedure of doing that, because it's something I need to consider, but haven't a clue how to go about it, or what the process/experience will be like. Thank you.