Steve thanks for the reply.
What is strange is that I have a RPi with
Address=hblink.dvswitch.org in MMMDVM Bridge
And that works fine with my mode change and tune scripts.
However if I use the same settings on on my netbook running DVSwitch it appears to work, no errors that I can see in the logs, and yet it simply doesn't work.
Perhaps then more the question is why DOES it work on the RPi?