Those papers seem to cover a lot of the material needed for STEP, though you should probably read through the A-level curriculum and see if there is anything you have not covered, as much of it is needed in STEP. Even after that though, just doing these papers will not prepare you for STEP - the best way to do that is to practice STEP past papers, see how good you are, and then keep practacing until you are good enough. There are other texts you can read, and there may be courses you can do, but it is unlikely that the CAPE will prepare you adequatly if you don't practice a lot of STEP papers themselves.