Curioser and curioser!!
I still couldn't install the firmware update despite DLing several times.
I reset factory defaults and turned off the routers firewall. No joy.
I then tried the DMZ again and BINGO I'm onto the menu screen for the servers!!
Why that worked this time I have no idea.
I just need to install the server specific DLs and I should be hot to trot!
Thanks Maz and Bonk for all your help I was getting REALLY frustrated.
e/ salutes.