You might be able to choose a different exam board for further maths, but I would stick with the same one, as you'll then get used to the style of question and what they're looking for in your working.
For a level maths, I'm doing the same as you.
For Further Maths, I'm doing D1, D2, FP1, FP2, S2, M2 (I took the first three this year). It seems to be a good mix, however if you get to choose your modules (I don't), universities seem to be recommending that you don't choose D1 and D2, but opt for more mechanics, statistics or pure.
Also, you need to make sure you do at least 3 a level modules. To check this, look at the specification for your chosen exam board.
Hope that helps!