O.K if you want Vet med, then don't give up!! You are far from being the only person that hasn't got in first or second time round, and apparently this year has been particularly difficult. Jimjamjess is going to Bristol in September after 6 years and 3 application rounds,and she's not the only one. I know it must be demoralising, but if you got to interview you're halfway there. I don't know what went wrong at this point, but maybe you could do some practice interviews with a vet. They're not expecting you to know much, but want to see how you approach problems. I didn't even really mention in detail the operations etc that I'd seen, because it wasn't me operating. I just kept to things that I'd done and learnt like coping with blood and owners in a variety of emotional states.
The schools do of course require minimum grades, but after that it's human qualities that they are looking for. Being a vet involves people contact, so work on your communication skills. Even if you don't feel confident, put on an act. Get a job that involves talking to customers, in a coffee shop, supermarket, bar or something. You'll be surprised how it brings you out of your shell. And if at interview they do ask you questions that you don't know the answer to, think about the animals welfare first and you won't go far wrong.
The selection process is very competitive, so not getting accepted doesn't make you a bad candidate and if you have the possibility to try again, then go for it. Saying "NO" to your dream career now because you think it's too late when some start their studies in their 30's or later would be sad.
Hope everything works out for you.