Have you seen these excellent, and reassuring A level notes for students from Mathsbox? These were made available some time back, my students really like them.
From the excellent MathsBox site, see: Pure Mathematics A Level Notes. The notes have a very comprehensive set of clear and well-explained examples.
Also available are Statistics and Mechanics Notes
— SandraD (@mathsbox1) April 23, 2019
Mathsbox has many free samples to try, easily one of the best value subscription sites around in my opinion.