Well firstly congratulations on your AS grades they are exceptional and you look like a very competitive medical applicant. However, whilst your AS grades are amazing there are some things you should consider
1. In terms of automatic shortlisting for interviews the ONLY things considered are GCSE grades and BMAT scores. No personal statements, no AS grades (nor UMS - which they don't even ask for in the first place) except for marginal cases. this is roughly how it works: Candidates are given some kind of score - based on 50% GCSE (consisting of half number of A*s, half percentage of A*s), 50% BMAT - and ranked by it. Let's say 1000 apply and they want to interview 200. (These numbers are made up) the first 160 are automatically shortlisted. They will then look at those who have some kind of special circumstances, and also the next say 60 applicants immediately below the shortlisted ones, and from these groups they will add another 40, to make the 200.
2. Your GCSEs are a bit below average for shortlisted applicants, which means you are at a reasonably substantial risk of being deselected. HOWEVER a strong BMAT performance can counteract this, but of course you won't know your BMAT score when you apply. Roughly 70% of applicants with 9 A*s are deselected, and roughly 5-10% of applicants go on to get an offer at the end. Also, GCSE scores are adjusted for school performance, so if you go to a poorly performing school that could effectively boost your ranking, improving your chances.
Though this %age is not great, I would say based on your AS performance you definitely have the ability to be in that 5-10% (someone's got to be!) But you're going to have to do well in your BMAT and shine at interview.
How come you are not considering Cambridge? Unlike Oxford they do not have a harsh shortlisting process. Also Cambridge cares a lot more about UMS/AS, which would make you attractive to Cambridge. I hope this hasn't sounded too harsh but I wanted to be helpful. You seem like a promising applicant who could get missed out in the shortlisting process, so if Oxford is definitely where you want to go my only advice is to put absolutely everything into the BMAT.