I got an 8 at GCSE, and didn’t do additional maths, but I am really enjoying a level maths and further maths. Its completely different to GCSE, but it’s much more interesting.
I got an A* in maths last year, and I’m predicted an A* in further maths. The thing that makes it harder is you have to completely understand everything. You can get through gcse with hardly any understanding and still get a decent grade, but at A level it’s not that easy because everything builds on everything else.
You'll do fine if you put in enough work throughout the year (not just near exams), and ask for help as soon as you need it with anything.