Jones & Couchman - I reckon the exercises are good practice
Cambridge Study Guide - Mainly cos my school used CSSA papers and it's gives a good indication of the standard of CSSA papers (as they're from the same people who write the CSSA trials)
However, I think textbooks can only offer so much. They're usually good for developing foundational skills as you learn a concept for the first time. Once you're familiar with the theory, textbook questions become really tedious...past exam questions are the way to go at that stage.