Well, 'learning in the country you plan to fly in' only really makes sense if you only intend to fly in one country; if that's what you want to do in a country as small as Britain, then I guess it makes sense. Personally, I can't think of anything more dull.
If you actually intend to use an airplane to travel, then I don't think it makes much difference where you learn, and you might as well do it in a country that actually appreciates GA a little, rather than the European hatred of anything a bit out of the mainstream!
Good weather, much friendlier people (in general), low costs, free landings, must I go on? I have flown hundreds of hours both in the USA and Europe, and have not found anything at all that Europe does better.
I got my JAR PPL in the USA, and found that flying in the UK and beyond was not appreciably different; certainly not enough that it required hours with an instructor, or anything more than revising the different RT procedures from the Trevor Thom book.
I'd love to hear, though, why you think there are advantages to learning to fly in the UK (apart from 'not able to afford the lump sum for a USA trip)?