Trig identities take a bit of getting used to I'll admit, but once you learn it it's very easy to spot the patterns. They're nearly always (if not always) proof questions so you always know what you're looking to get.
I also find differentiation one of the easiest topics, and anything to do with stationary points I really like (I'm a very sad maths loving person
)
Don't be nervous as I'm sure you'll find it ok. It's not that much more than what you have to do for GCSE to be honest, and most of it actually makes a lot of sense the first time round.
Are there any other topics you struggle with/are worried about as I'd be happy to help you