i do edexcel maths, and i've honestly never tried the CGP book for a-level maths, but i haven't really liked CGP books in the past, i used them for gcse science briefly and tried it out for a-level biology and personally felt like the content was too simplified.
i honestly have no idea what's inside the a-level maths cgp book though, it could be very good but my school uses the pearson edexcel a-level maths textbooks. they have SO many questions and worked examples, which i honestly use religiously for my maths revision.
i don't take FM or physics, but for chemistry, (i do OCR A), i use the OCR textbook, we use online versions on a website called kerboodle, but there are obviously physical copies, and there is an AQA version of it.
the CGP one may be good, but in comparison these textbooks i use for sciences i find to be a lot more in detail and it just helps me learn better as i like how detailed they are. however the CGP books are honestly not bad, it's just that i personally don't enjoy using them that much but they can still be a great resource, especially if you have the workbook or whatever it's called too!