I studied A-levels so I don’t know if my advice will help, but from friends who wants to study medicine, the grades that most universities, especially the prestigious ones ask for is A*AA to ABB. Having these grades in Biology and Chemistry is recommended. Math is optional from what my friends told me but I’m not sure. From an A-level perspective your grades are really good, so do international students have easier exams than UK A-level students? Also I applied to King’s College for a different subject and they required AAB and my predicted grades were A*AC and I still got an interview.
I recommend speaking to your teachers and the universities where you want to study directly before you make any decision. Resitting is pretty big decision and time consuming, so you shouldn’t do it if you don’t have to. Just speak to the universities and see what the best next step is.