Well, you'll only know if veterinary is really for you if you when doing work experience. You don't only need Bio to get in am afraid, you also need Chemistry. Try get some dairy placements, work at small and large animal clinics, kennels and/or cattery, lambing... getting your hands dirty is important, and although you may strongly feel that veterinary is the career for you, you may well change your mind when you're waking up at 4:30 in the morning to milk cows, or see an animal being PTS (and realising you will have to do this one day).
I think Nottingham has a prelim year if you did no science A levels, but it's quite difficult to get in to. You should look it up though.
Otherwise your best bet is taking a year off to do Bio and Chem A levels, whilst simultaneously doing MUCH more work experience. (Look up Liverpool's work experience minimum, and strive for that if not more as many applicants will have started doing placements from a ridiculously young age).