They are great grades! Bearing in mind London only consider these and not your AS results (plus, as long as you are predicted 3 A's and get get enough BMAT results
)
What did you get in maths? Bristol rejected me as I only had a (very high) B at GCSE, even though I was offering it at A level!! And they had never specified this on their page! The Unis can be really sneaky and they will find any way to reject you apparently! (Not all are like this, but honestly, feedback from can be good, and pretty bad that it is no help whatsoever!)
Also, gateway programs are for when you don't have Chemistry or Biology A level (this varies between Uni's!)
Have you looked at Year 0 in Liverpool? You don't take A levels, (assuming you haven't already?) you apply and you do a year of science, then you move on to Vet med
I think it guarantees your entry into it, but they get about 3000 applications for it!
My school let me down too, I constantly asked for help and never got it! Plus, they didn't want me to do Veterinary neither, they made me drop maths at AS instead of letting me dropped technology, then tried to push me into Engineering or Medicine. Ridiculous, so I know how you feel!
Gap years are great, though planning them is a pain!!