As someone said above, it does seem easier than most of the other subjects at A-level. I've always found that maths is my strong point so if you feel the same since you're predicted A* it shouldn't be too difficult in any way, as long as you stay on top of it and don't fall behind. I don't mean to brag, but I barely did AS Maths revision for my own reasons and I just got over an A (not that I recommend you don't revise). It did mean that I could focus on my other subjects a little more though.
If you do find AS maths a breeze then A2 shouldn't be significantly harder; you just learn more techniques and rules and you just need to learn how to use them. The only form of revision i've done for maths this year is past papers, especially over Easter hols and i'm set for A* if not close to full marks.
My advice to you is to learn a bit on basic differentiation and integration in the summer. Don't over do it because it can get quite complicated if it's new to you and you haven't done it before. The reason i'm suggesting this was because at GCSE I also did the FSMQ which is at a difficulty between A* GCSE and A-level maths and it had those topics in. What it meant though was that when it came to AS I already new about them and it made life so much easier.
Good luck with GCSE and feel free to ask if you need to know anything else.