The best solution for your wireless needs would be to link your Home Hub 5 to your Billion as an access point. You may wonder why not use bridge mode but I prefer the 8800nl as a router as you can give the LAN Devices a static DNS server e.g Google DNS, and I like the performance of the 8800nl
To do this First set up your Billion 8800nl and make sure its connected to the internet.
Disable WiFi on the 8800nl as we will be using this as the router and the HH5 as the Wireless Access point.
Get a laptop or a PC and connect to the HH5 via Ethernet, enter the advanced settings.
Now disable all of the router settings on this like.
-uPnP
-Smart Setup
-DHCP server (most important)
-any other router options, I cant remember them all
Now enter the LAN Settings for the HH5 and change its IP to 192.168.1.253.
Now this allows you to access your Billion with 192.168.1.254 and the Home Hub 5 with 192.168.1.253. Giving easy control.
Now hook up your home hub 5 to the billion via the Ethernet ports on both the Billion and HH5 (Gigabit preferably) and you will have pretty rock solid WiFi performance via the home hub 5 using the 8800nl as the router.
Also ignore the flashing lights on the Home Hub its just because its not directly connected to the internet, and is now instead getting internet via the LAN port.
Good luck!