Thanks for the EIMACS suggestion - I'd only seen their expensive logic courses, and hadn't realised that they also have a cheap calculus course. I'll look into that!
Books are not really what I'm wanting (I have some, but largely for practical reasons - he'd have to carry them around, and carrying even the rather small GCSE book last year taught us the disadvantages of that! - even good ones aren't much use to me right now). But now the thread is here and maybe someone else will find it useful in future.
