The A-level textbooks sound like they're old spec, so I don't really know what you could do with them. Schools will probably have the new spec textbooks; maybe an A-level maths tutor could put them to good use? They're not massively out of date, they're just missing bits and pieces of content, and of course their organisation is completely different to the new spec.
As for your copy of Spivak's *Calculus*, which edition is it? I might be interested in buying it off you if it's not already spoken for, and I'm in the UK so postage would be reasonable.