I'd agree with the above. A friend of mine did work experience at a vet's for years whilst she was at school, she even did animal jabs etc by the time she left. She also got straight A's in every subject at GCSE and A' Level but she still only got accepted by one university!!
The others rejected her, and she didn't set her sights ridiculously high in terms of where she applied. She did pass in the end but the last I heard she was finding the hours quite gruelling and tiring and travelling to find an ideal job meant being away from her friends and family which she also found hard.
I would advise volunteering in animal work of some sort a.s.a.p - even if you don't end up applying for vet school you'll probably enjoy it and it will give you an idea of what working with animals entails. If you *do* end up applying, the work will be a necessity on your c.v. You will definitely need to excel at Science subjects and be a good all-rounder too.
Am not trying to put you off, just trying to be realistic for you, lol. If you can do it I think it's a great thing to do. A truly caring vet is a precious commodity in this world!