My collie has arthritis and at some of the winter agility shows we are going to I hope to be able to keep his joints a bit warmer to stop him getting so stiff. Are there any good products out there that people could recommend? I am planning on investing in a really good thick coat for him, but I am hoping to put something on his legs to keep them warm too. Someone recommended hand warmers wrapped in bandage to keep them in place, which I may try. Anything else that I could do?
Thank you...

I was going to suggest the same thing. I had a heated blanket pad, I think from hub international and it simply sits under the coat which is fastened well.

Keeping him standing or lying on a piece of vetbed wil do the trick.  I have sat on it on a cold concrete floor and you don't fel the chill through it at all, as you do therough the non thermal soles of my shoes!