The first choice is always to go to med school in the country where you want to practice. 8 years combined of college and med school in the US may be prohibitively expensive for you compared to its equivalent in the UK (where I know schools are MUCH cheaper). Gaining a residency position as a foreign medical graduate is a dice roll, I think something like half of applicants are unsuccessful. Pursue it only if you have a solid backup plan you'd be happy with in the event you're blanked.
Unless you're looking at this as a means to emigrate to the US, in which case, you've nothing to lose.