I don’t know why people think CGP are trash for A level.
I do OCR A level Chemistry and I have the CGP revision guide and their workbook for practice. And I guarantee you if a person memorises only the CGP book, do some practice question. There is no way he is getting below an A/A*. In fact I believe the only book you need for OCR a level Chemistry is the CGP guide. Then Practice, Practice!
The downside of OCR CGP book is calculation topics. The book fails to show you the complicated calculations and they just throw the forumla so you don’t understand the calculations. If you really want a book to understand calculations in chemistry. I recommended buying “Calculations in AS/A Level Chemistry” by Jim Clark. Then ask your school teacher for Chemsheets for calculation topics.
Even for a level Biology I would say that if a person memorises the whole cgp book. Then Practice Question! He has a good chance for an A. A* I don’t know because most of OCR Biology is application. This again back so up my idea there is no point wasting time on the books provided by the exam board because they contain so much information while the exam is mainly going to be application. In fact our Biology teacher strongly suggest to revise from CGP book.