Don't listen to what people say about the emphasis of GCSES. You have made incredible progress from GCSES to AS Level- a lot of people find the change difficult so many people under perform in their AS Level exams. Unis will see your progress and this will be a certain factor, as long as you continue to perform outstandingly and set optimistic goals. I believe you have a shot at the top unis for medicine as long as you show your ability in the UKCAT/BMAT. However, if you didn't get at least 10/11 A-C ish at GCSES then some unis might be put off even if you've made excellent progress.