Sorry everyone, one last thing.
As mentioned in the original post, my fourth subject (psychology) isn't offering an AS exam at the end of this year due to complications on the schools behalf (there was no psychology teacher for half of the year so we were unable to finish the course in time). Therefore, all students taking this subject are required to take the AS exam at the end of next year, even if they were hoping to drop it after Year 1, as I was (if that makes any sense). However, many Medicine courses require an AS grade at grade B or above at the time of application. Of course, I'll hopefully be getting that, but not until the end of next year. I'm assuming this is something I should mention on my UCAS statement (i.e. something along the lines of "I was unable to sit the exam for my fourth AS this year due to complications blah blah blah...")?
Thanks all.