Fixed the problem, here's how.
1. Looked in SAMBA log for machine I was logging in from and saw entrys saying that the machine name wasn't recognised.
2. Followed SAMBA howto by Darrell May at
http://mirror.contribs.org/smeserver/contribs/dmay/mitel/howto/samba-howto.html and deleted the machine name entries for the 2 PC's in the network. I also saw reference in the log to an alternative name for one of the PC's I used when trying to join the domain which I also deleted
3. Rebooted the client PC and logged in successfully as a user. Unfortunately Windows had trouble with the roaming profile (new profile directory started with a 000 suffix) Pulled out the network cable and logged out (so e-smith server copy of the profile not corrupted), logged in as local administrator, and added user as a user on the domain (with admin rights which seems to be necessary)
4. Logged off and administrator and back on as user, success.
Life is good again.