Erm.. 'Philosophy: The Basics' by Nigel Warburton is good when you're just starting off a module, but it's not really worth buying because of its lack of depth so try and borrow it from a library if you can. Actually, it might be ok to buy - I borrowed it and used it during revision because it summarised the main points, if you get what I mean (sorry, I'm rambling here). 'Think' by Simon Blackburn has some good basic Epistemology stuff (it's best for Philosophy of Mind at A2, but I guess you won't be needing that) and was particularly helpful for Descartes, but again it glosses over the details. Actually, because you study a single text in a great amount of depth, make sure you have a decent secondary resource for that. For instance, for Descartes I borrowed John Cottingham's book, though I can't remember what else I used. For the Ethics and Epistemology modules, I found the 'Routledge Contemporary Readings' series great because they collect together the different perspectives on philosophical issues you'll need to raise in your essays. Of course, I don't know which modules you plan to study (as far as I know only Epistemology is the only compulsory module as a foundation to Philosophy) so I'm not sure how useful that will be to you.