If this ever happened to someone in the high school (I wasn't aware of it happening to anyone in my college haha
) I went too, what they usually did was allow you to sit one in the morning and one in the afternoon.
However, this meant that the person would have to be in isolation all day too. This was to prevent cheating. This is because, if, lets say, you sit the History exam in the morning, and the other in the afternoon, and they let you out between the exams, you could go tell all the other History students what's on the paper as you've already sat it and everyone else won't have.
Although,
every school/college is different, so your college may have a
different approach to dealing with this issue.
I wouldn't panic yet though as it's still a way off. I'd speak to you're college about it if your really worried about it. I wouldn't bother e-mailing Edexcel - not their problem! It may bring it to your colleges' attention too as other students may also end up having this problem.
Good luck and hope you get it sorted!