That's getting close, and in fact other products at that site are closer. However, none of them quite do what I'm looking for - a 4 channel stereo mixer. It doesn't seem like such a lot to ask for but nodody seems to make them! The closest I've got:

http://www.maplin.co.uk/Module.aspx?ModuleNo=31137&criteria=mixer&doy=21m2

However that seems designed for Mic inputs, and the SNR is terrible.

I'm going to have to make my own :-(

Rob