I installed DynDNS client and using Port Scanner worked out that the only open port is 53. So, I "rooted" the phone in order to use ports <1024. Then used Port Forwarder to pass port 53 to my Linux box on port 80.
I can ping [link removed] from the device running the web server, so the "uplink" appears to be working.
The DynDNS client does have a message, "You are connected to the internet through a proxy. This probably means that internet users can NOT connect to your device".
I can see my IP being updated on DynDNS but I can not access my web server remotely. So, maybe that message is a clue but I don't know how to fix it!
I am on prepay, if that makes any difference. I have an incident filed with Telecom, but no answer after 3 days.
Thanks for any tips.