You seem very determined to apply to medicine whatever we try to say, no matter how truthful we are being. The step up to A-Levels is huge for the sciences (I do bio and maths) and if you're saying timing is an issue for you at GCSE, it will be a major issue at A-Level if you don't sort it out now.
You HAVE to get AAAA at AS to stand any sort of chancellor getting in AND do really well on the BMAT/UKCAT. Unis might say that GCSE's don't matter but they're more likely to accept someone with higher grades than you if you do the same on your aptitude test and AS.
I personally think you'll struggle at A-Level but you're not about to listen to anything I say. Biology A-Level is HARD, Maths A-Level is HARD and all my friends say Chemistry is HARD. There is a reason why my college doesn't really let anyone apply to medicine without a GCSE points score of 6.7 and it's because you're just not likely to get in anywhere.
I know it's not what you want to hear but it's reality