I did the same qualification as you and got an 8 in the real thing. For A Levels I chose Bio Chem and Maths (for med too lol), and Maths was by far the hardest subject. I loved it at GCSE, but A Level Maths was the worst, like really really hard. I’d say to some extent, yes you have to enjoy it, but if you’re not super confident with your skills or you find other subjects suit you better go for them over Maths. Also, I’ve seen people saying doing maths will help you with BMAT and to be honest, I don’t think it gives THAT much of an advantage- for me a lot of the methods I’d learnt at A Level are now completely different for the BMAT GCSE spec/a lot of content I was taught at GCSE wasn’t covered at A Level, so I still have to go over them to remind myself (I’m taking a gap year and reapplying).