go to uni or resit and reapply (med?)

im meant to go to surrey to study biology but i dont know if i should resit and reapply to better unis and/or different course too. i was originally going to apply for medicine but changed my mind when my mental health started deteriorating. part of me still wants to do medicine but the ucat and competitiveness makes me think
i got 999998887 at gcse but BBC at A level. i do think my grades will improve if i resit.