In terms of chemistry then, just text book end of chapter questions then?
Um, not exactly. You can get some good revision resources from physicsandmathstutor.com. I've worked on them, end of chapter questions and the past papers.
Yes, can't speak for biology 100% but for maths and chemistry it's just grinding questions and watching the occasional youtube video. Biology requires a bit of memory from what I've heard and tons of past paper practice to really get a feel for what the examiners want, but it seems doable.