Varies from exam board to exam board. Recently, I've been doing animal behaviour and evolution within B3, bits of everything in C3 (I've been getting ahead) and eyesight within P3.
I've been doing C3 work at home, and a bit of B3 work at home. And yes, I have CGP's Edexcel revision guides, and they are really useful. (to the point you could probably learn the whole GCSE from the book!) I have been making my notes based off them