Hi, Sophie,
The veterinary profession in the UK is very small when compared with, for example, doctors or lawyers.
The veterinary graduates cost the most to produce - not nearly all of it covered by student fees. We cannot afford - nor would we wish - to produce veterinary surgeons who cannot get jobs. As it is, veterinary graduates from any veterinary school in the EU are entitled, under the terms of the Treaty, to be eligible for employment as a vet in the UK.
The end result is that UK University veterinary schools can select the best qualified school-leavers for admission to the veterinary course ( I note that you do not have Physics, which is essential as well as Chemistry and Biology)
If you look back on this site you will find some information about interviews at the vet schools.
W