I would say take all 5 and then drop one if need be - it's much easier to drop a subject than to take on a new one. I did well at GCSE (almost as well as you as I did less subjects) and started with 5 subjects, including maths and further maths, dropping my essay subject at AS to focus on my remaining science A Levels. I definitely think English Lit would be good, at least for your first year, since it's a nice break from the sciences and teaches you valuable essay skills. If you can make your writing sound better then this will help you for life.
For medicine, unis will want to see chemistry and biology for certain, and possibly maths - anything else is up to you. Personally I love physics, but if you're only taking it because it looks good and you don't really like it then it may not be the best choice; it shows logical thinking and some of the medical physics you learn in the end of the course would be useful, but it's not essential.
Judging by your GCSE results, you're pretty smart, so I'd say take them all and see how you do / which ones you are better at.