when I was 18 i was also between things: first thought to go to a bank (mighty glad I didnt), then went abroad (London incidentally), and stayed in UK for all my studies. I always wanted to study though.
as for London: I went for a language course but like Mooks said, you are talking money, when you want to live there. for me this was 10 years ago and I believe it hasn't gotten any cheaper
. if you dont want to study now, or ever, don't. although I believe in studying, big time, i have had students who didn't want to be there, and it isn't helpful. I say, take the year off, no matter what you do, and you may find then something you would prefer. you could try fashion of course, and there are many options, maybe magazines (RUNWAY, lol), or even the big high street shops like TS, etc. (i am not saying in sales but in the HQ, maybe part of designs, being a buyer etc). if you really want that, go for it.