Definitely get the 4000Q book. Thats what I used and I got 6.9 5.8 and 4A (although for vet med not medicine!). You may also want to revise over gcse from all boards again, as certain things in the questions were not on my board and so I didn't know about them. Also, not sure whether you have done double/triple science but if you did double (like I did), then revise the triple content as well as that is new - some of it came up in AS.
Hope this helps!