I suppose it would depend on what the problem was, and how immediate the need was.
For example: I have a kidney disease, which will eventually cause my kidneys to stop functioning. There is no "cure" but there is the option of dialysis or transplant.
In that case, I would likely return to the states as I have tons of friends and family who would opt to be live-doners. Plus, that is where the "best" specialists for my particular kidney disease live/work.
Example two: I have a rare "blood disease" that can/will cause all sorts of havoc down the line. If I needed life saving treatments, I would stay in the UK.
I would likely stay for most reasons, only returning to the states if I felt that, for one reason or another, there was a bennifit to that.