The USA option is OK (I did it for my PPL) but it will be the hardest work you have ever done (flying, studying for exams, taking exams 7 days a week until you are done).
I'd have to disagree a little with this; I took the USA option, did all the flying and exams while I was out there, and it was more like a holiday than a period of hard 'work'! You do have to be dedicated, but you're flying; thats not work, its *fun*! The exams are all pretty basic and common sense, as long as you make sure to read the material properly.
I heartily recommend the USA option, agreeing though that you'll take a few flights to get use to UK procedures on your return. Aim to go for 4 weeks rather than three and it'll be even nicer
Compared to my experiences at, say, university, the work level was low.