Sounds like your on the right track to get into those kinds of degrees. You might be best talking to a teacher at you're sixth form/college what your going too. They will be more knowledgeable on each degree and help you decide which A levels are best for you. I would advise Biochem- bio,chem, math and art just to show your versatility and for engineering- math, physics, chem and art again for the same reasons and in both cases drop art at AS. My friend is doing biochem and genetics at nottm and she took bio,chem,phy and math and dropped math at AS