I am in the lower 6th right now and im taking chem, bio, maths and french, its a really good combination and I really enjoy it. For your fourth, do something you like and have natural talent at, because it will make your life easier workload wise, although anything for the 4th subject is fine. a friend of mine is doing chem bio maths and geoggers and likes that, so whatever if best for you. essay subjects- i dunno, it depends if you like essays and are quick at them-they could help for the BMAT, but will increase your work load in the lower 6th.
Does anyone know if UCL offer AAA or AAB because I have heard both.