you will have around 6-7 months on this course, im sure you'll be fine! overall, they are all mostly the same, but some schools may take different exam boards for easier/more lenient mark schemes (eg apparantly a level ocr bio is quite annoying with the ms) or maybe better grade bounds (eg gcse bio 60-65% was a nine). I know at this grammar school they did edexcel gcses tho.
You probably won't have to revise anymore than you usually have to for aqa compared to edexcel