No Wireless Detectable - Billion 7800N

I have a 7800N combined adsl2+ modem/router for about the last 3 months. About 2 days ago I came home from work to find the Wireless Network had dropped, although the green LED on the modem was still on. Since that time I have been unable to connect to the Wireless network, or even have the network appear on the list of connectable networks. I have two laptops a smartphone and the wireless network is not detected by any of these devices.

Nothing has changed with my WLAN setup, no settings were changed by me, no new devices recently connected. My main PC is connected by an ethernet cable and has not been affected, it remains connected to the internet at all times with no issues.

Things I have tried:
* Turning the router off/on
* Unplugging the router for 1 hour
* Changing Wireless Channels (Auto, 1,6,9,13)
* Disabled and Re-Enabled WLAN through modem settings page
* Changing ESSID Name
* Hiding ESSID then Re-Enabling ESSID
* Changing WPA2-PSK Passkey
* Isolating modem on phone line
and finally, Restoring to default settings, and starting all over again.

I live in a small apartment block and typically have 6-8 other low strength wireless networks in the list, and thought something may be conflicting with another device, however after changing channels 4 or 5 times I gave up on this thought.... None of the above resulted in the Wireless network being detected and displayed in a list of connectable networks. The wireless light remains on, and flashes periodically, but for all intents and purposes no Wireless Network seems to exist.