hey bro,
first of all, from what i know, the universities dont know that yu resat any of ur exams, why?
well, let's say u get a B in biology this session, and re-sit it in November and get an A*, cambridge will produce another certificate with ur new grades, so i dont think u need to worry mate, do ur best this time, and if (god forbid) u got bad marks, study well (start from september) and inshala u will get into the university u want,
and By the way, if u want to go to business school, why are u taking the three sciences ?
wish u the best of luck,
thanks