Sam, this is fantastic, thank you! I have set my ‘enable insecure guest logons’ back to ‘NOT CONFIGURED’ as that is how they were originally. Then I set up my T:\ drive again as a mapped network drive, this time, as you suggest, connecting using different credentials, and immediately have full drive access of the Tormach drive to both my computers.
I am very grateful indeed. My wife said I was getting a bit stroppy! And you have just fixed me. Thank you.