I've written a reply for you and have somehow managed to delete it!!!
I would recommend CGP books, which we found very useful when preparing for 11+. Have a look at their 7-8 Practice Books and Assessment Tests:https://www.cgpbooks.co.uk/Parent/books ... book_E3QE1https://www.cgpbooks.co.uk/Parent/books ... book_M3QE1
They also do books for CEM-style tests, but to be honest, for maths it doesn't really matter which one you use.
If you were to find any areas that needed more practice, I would recommend Collins 10 Minutes Tests for maths and English, as they have sections organised by topic. Finally, Schofield&Sims English Skills, Mental Arithmetic and Problem Solving, first books from the respective series for Key Stage 2 (or the last books from the Key Stage 1 series - for year 2).
If you haven't found it yet, here is a link for King's College School 7+ and other age groups sample tests:https://www.kcs.org.uk/admissions/seven ... nce-papers