VCDS-lite can be ordered and delivered online from ross-tech for US$99 so about £60 I would think. It should work with the ebay cables OK. I got the unregistered version of VCDS-lite with my cable and it does work, just most of the really useful things (resetting adaptions, recoding stuff like alarm settings, pairing keys, logging anything but blocks 001 - 025, throttle body resets) are not available on the unregistered version.
I also have a basic
OBD-II code reader which, like sambryant, I just keep in the glovebox

I posted a thread in the VAGCOM section asking about basic code readers, have a read of that. There is a good one from a company called Autel I think which is about £40, it's a bit more VAG-specific altho the one I got works fine. The guy that told me about the Autel one only did so after I'd already bought the basic one for about £20 or I'd have spent the little extra and got the better one!