There's no reason why you can't get into medicine without any A*'s! The most important thing for you to focus on now is getting at least AAA at A level, because you do need 3 A's to get in.
Yes, you want to probably avoid applying to medical schools like Cardiff that rely heavily on GCSE. But there are only a few that are GCSE-heaving. You have plenty of options, and you can only apply to four med schools.