Thanks for this. Other priorities have pushed this down the list recently.
I have the most recent firmware on both the ADSL modem and the firewall, I have some joy in that one of the addresses in BT specified range is mapping through the firewall. What I can't seem to be able to make work is to get the BT connection to work on a Static IP mapping, it seems to only work if it can dynamically assign the IP address to the firewall.
The ADSL modem is configured to Bridging mode, but I wouldn't know how to determine if it is hogging an IP address - I am not techie enough.
The BT Business Hub is a great piece of kit, I think it is some 'Smart-Alec' network configurations that don't let it support what I would expect to be a fairly normal requirement - BT's tech support chaps (third-party) were very willing in their attempts to help, but no one seemed to have the answer - they eventually said that it would not support what I was trying to do and that "the service is designed for use as a network hub and not a bridge"...
The irony is that the Easynet WAN (ADSL) connection is configuring with static IP addresses with no problems, so I know it is not the firewall, it could be the configs on the Lucent Router (Easynet managed) that are smarter than the ADSL modem with BT's default network configs.