Still not able to access your router. Remove R1 from DMZ. Then can you port forward 1024 - 60,000 TCP to the R1 on your ISP hub please.
I'm not sure what else to do Fraser, I dont have an ISP hub or DMZ, the duma is plugged straight into my cable modem. I have factory reset the duma and made sure remote support is ticked, nothing else is turned on. Please try again.