I did biology and maths at A level. Biology has a large amount of content to learn so out of my subjects (bio, chem, physics, maths), biology had the largest workload. Maths wasn't too bad workload wise. A lot of the early topics in year 12 heavily overlapped with some GSCE content so they were pretty simple (for me at least). Consistency is key with those two subjects. Make sure you make notes from the start, create revision resources from pretty early on and do lots of practice exam questions as part of you revision.