Do you have to take 4 at your school ? I would try to do 3, but not including further maths as medical schools don’t accept fm as a suitable third a level with maths as well.
Many unis ask for chemistry and one day other science out of biology, maths and physics, but biology would leave more open to you. I just think that, if you really want to do medicine, then why limit your options now ?? There could be places that ask for bio and chem, that you would be guaranteed an interview at with your GCSEs or ukcat, yet you would have cut them off already. You should look at uni websites to see just how many want biology and chemistry.
I would take chemistry, biology and maths or chemistry, biology and psychology. Doing further maths will not get you anywhere, because it tends to be only suitable as a forth subject and (I’m not sure, so maybe do research on this bit) I think that could mean your offer would only include grades in your other 3.