If you're mainly teaching yourself, I recommend MyGCSEScience online. You have to pay to subscribe, but you get videos of all of the biology, physics and chemistry papers, and also practise papers for each topic. It has definitely saved me this year. If you just want a revision guide, the CGP ones are amazing. I have them for all of my subjects, and they make everything so simple. They cover all the required practicals, and also all the math skills you need.