Before AS, I chose:
Maths
Physics
Chemistry
Biology
Philosophy & Ethics.
Just before classes started, I changed to:
Maths
Physics
Chemistry
Biology
French.
Then I dropped French. Then I dropped Biology. Then I did my first lot of AS exams. Taught myself AS Further Maths.
Dropped Chemistry after getting a B, kept going with the other 3 As.
Now I'm on Maths, Physics and Further Maths and I've applied to do MMath Mathematics (or MSci at a couple of unis). Hopefully going to Bath or Exeter.
...also, if I was on Edexcel or OCR MEI I'd be getting AS Additional Further Maths, but my 3 extra self-taught modules don't really mean anything because I'm OCR.