A-Level Computer Science

I am doing Computer Science along with Maths and Geography as my A-Level options and im going in to my first year (Year 12). I havent done GCSE Computer Science but have good interest in the subject.

Does anyone have any advice on preparing for it/ any courses that will introduce me to the subject?

Make sure u put a lot of effort into the coursework and just work hard for it, bit generic but oh well. It'll probably be your hardest a level.

Would it be harder than maths (I got a grade 6 in Maths and 6 in Geography but havent done Comp Sci)