Bangor University GCSE Revision guides?Watch
My child has been using the Bangor notes, as well as the "My Revision Notes"/"Fy Nodiadau Adolygu" series from Hodder. Both sets of resources are excellent.
If you're doing the paper 2s alone this year (maybe you did the paper 1s in Year 10), just remember that some of the paper 1 knowledge is presupposed in paper 2. This only happens in some topics, but it may be worth your while to look back on your Year 10 stuff.