Honestly I wouldn't consider jaw surgery in the UK, the surgeons here aren't as skilled as Europe or the US.
I would recommend you to see Joan Birbe in Barcelona, he has some pretty impressive results and his prices are very reasonable. Nice receptionists who reply to emails quickly (although their english could be better, its good enough for most cases I would imagine) easy flight out to there from the UK. Birbe definitely knows what he's talking about, he's a very knowledgeable guy that picked up on a few issues of mine that other surgeons either didn't spot or didn't think to mention (both bad).
You can also have sleep apnea tested there for 200 euros, this of course means staying for a day or two so perhaps would be wiser to get it done in the UK. You need to register at least 5 hours of stable sleep on the machine which can be a little bit problematic (hotel noises etc) I failed my first test but managed just over 5 hours on the second. I was staying 3 days to see Birbe and Alfaro so it worked out pretty nicely.