I am not a vet med student (my friend is and loves it) but there is only one answer: Bristol.
This is doubly if not triply true if you are particularly interested in large animal practice as you are right in the West country where small, medium and large 4-legged animals are found in abundance.
There is a regular bus service between Langford and Bristol with extra laid on for students if necessary as I understand. The nightlife, well, it can be pretty 'animated' if that is what you are interested in. It is a huge and richly diverse city to which anyone can themselves feeling at home.