Okay if I had sat down and thought about this, I might have figured it out.
I decided to get an 'office line' and picked up a Cisco 7940 with a SIP Firmware and subscribed to a 2talk service.
After a bit of fiddling, I managed to get the phone dialling out and all was okay, then I tried to call inwards with so such luck.
I read a bit of material, but it does appear to get SIP going I need to open ports, but of course I use Orcon Genius which also
uses those ports for SIP...
So I can see no way that I can have a SIP phone behind the Orcon Genius router, unless there is some registration for Port numbers.
Any VOIP expert opinions out there?