Back to the OP's question.
I've had a lot of PMs lately from US trained/training MDs who want to practice in UK. I'm going to throw up a website with advice on how to do it ("first aid for UK residency training" - I'll be rich I tell you, rich!

)
In the meanwhile you could check out my posts in the UK forum - highlights are:
a) Come sooner rather than later. US residency training won't count for much over here* so you are better coming straight after medical school and getting into the system early.
b) Debt is a b'atch. UK salaries are reasonable (30-60K pounds during training, = 55-110K dollars, and 60-120K pounds when fully trained =110-220K dollars) but might not be enough to service massive US loans - especially given higher cost of UK living (think US big city prices rather than midwest).
c) Training is longer (but hours are shorter and pay, as above, is better). 5-9 yrs postgrad training rather than the 3-7 typical in US. You'll work less hours during this training though (<60hrs) and be paid much better (55K dollars as a intern is about standard).
d) You'll face some hurdles. People are mean to FMGs everywhere. (For reference= The stereotypes of US MDs are: no bedside clinical skills, over reliance on expensive tests, ordering shotgun hundreds of, rather than focused, investigations and unmerited arrogance. In my experience about as true as every FMG doctor in US being rude, having poor judgement or being unable to speak English - ie: not so much.). You get over this and if you are a good doctor people will respect you no matter where you went to school (just don't expect it to open doors for you).
e) The best place to look for PGY1 jobs is BMJ.com jobs site or via the "deaneries" themselves. (training positions organised on regional level rather than by individual hospitals or universities). a list can be found here:
http://www.mmc.nhs.uk/pages/deaneries
Good luck - the UK is a great place to do medicine and a lovely place to live. You might want to consider doing a summer elective here to see how you like it before you make any life changing decisions though
😉
All the best,
W4G,
*not a reflection of US training standards just of the fact that the systems don't mesh well.