Moving schools for A-Level

I am currently at a girls grammar school in Buckinghamshire (Bucks grammar schools being selective and state-funded) and in my first GCSE year. I have been thinking lately whether I should move schools for 6th form to Magdalen College School, a fee-paying high-achieving school in oxford. I want to study medicine, and while my current school is very good, several things attract me to moving: a) grade insurance b)high support for getting medical hopefuls and c) the social scene and oxford itself (seeing as I am at a girls school in Aylesbury...) Advice??