Your GCSEs would be weak for an Oxford application. They use a sliding scale based on the percentage of A*s you have at GCSE, along with your BMAT result. They are not really interested in AS grades. You have less than 50% A*s, and I believe the average successful applicant has over 90%, so you would need to put in a completely stonking BMAT performance (i.e. in the top few % of applicants) to even stand a chance of getting an interview.
If you perform very well at AS, you might consider applying for Cambridge as they focus more on AS UMS marks rather than GCSEs. Taking Biology (and, if necessary, dropping F. Maths or one of the other non-sciences) will increase the number of other medical schools you can apply to.