@stevehillnz, maybe: http://themacadmin.com/setting-a-default-paper-size/ from @milesleacy

This has changes slightly in 10.9,
the domain is now org.cups.PrintingPrefs and the key is DefaultPaperID

Thanks I had seen that post and run the command without success. I just ran it again for good measure and this time it worked. Pilot error on the first attempt by the looks of it. Thanks for your help.