I've contacted the school to see if they have any advice. They hadn't mentioned anything about UCAS but I just happened to find it somewhere. He is starting year 11 next month and his cohort in the UK is a term into year 11. For him to do GCSE, he would have to drop back a full year so will be with younger kids, which he will not like, plus I am unsure if this is even possible. He will already have to do an extra year of school with A levels- he's not keen to move in the first place, so this will totally put him off! I'll see what the school says....