Where can I get apple and plum/peach rootstocks for grafting?
You could try this site :
http://www.brogdale.org.uk
Don't know where you are but they are in Kent and very helpful.
This place sells them:
http://www.blackmoor.co.uk (http://www.blackmoor.co.uk)
scroll their home page right down, there is a rootstock link.
Thanks guys/gals. V. good links :)