Looks standard set of subjects for medicine so will be fine. Chemistry and Physics i would say are the biggest jumps from GCSE to AS. They are perfectly sensible choices for keeping options as widely open. I doubt any places really care if they are just sciences, since they are good subjects regardless.
For Oxford, i think their medicine is A*AA. You won't find any medical schools with lower than AAA as their standard entry requirement lets put it that way. (Though theres probably 1 thats AAB)
Impossible to tell if your 'suitable'. Grades are good but you NEED NEED NEED work experience, otherwise you won't even get an interview/offer. Also theres a test called UKCAT for medical students but you won't need to touch that until Y13.