You can buy Bill's latest album, which is a 36-track retrospective called "Unicorns", direct from the man himself at www.billcaddick.co.uk! I have it and by God it's good! As far as I know it's not had that much distribution, so that's probably your best bet as I haven't see it in any record stores or even on Amazon. As regards his solo stuff from the 70's and 80's it's all deleted, sadly, so unless you can find any second hand LPs, you're unlikely to get hold of it anywhere.

Good luck

Chris