I have got something similar (but a little more complex) working OK.
All IP addresses start 192.168.1.
I have 2 * O2 lines, both with WAG320Ns (Bridge mode. IP 192.168.1.4 and 192.168.1.5)
These both attach to WAN ports on a cheap load balancing router (TL-R470T+) 192.168.1.3. This is the DHCP server.
This has 3 LAN ports - going to Wired ethernet, Powerline and a TD-W8960N (192.168.1.2) working as a wireless access point.
The next bit should be relevant to you.
I have a 2nd ethernet cable from both of the WAG320Ns connecting to LAN ports on the wireless AP.
The DHCP has fixed addresses for everything, with other network devices starting at 192.168.1.80.
With this setup, I get full network access to the 2 Bridge mode devices.
So, for you, I'd say you could connect a 2nd ethernet cable from your bridge modem to a LAN port of the router, and assign a fixed IP address to the modem in your DHCP.
As for me, I'm hoping to get FTTC in a month or so, and go back to just 1 wireless router, (probably with a wireless repeater).
Edited by deleted (Tue 04-Dec-12 01:21:08)