Got the above mentioned connection working well after initial unhappiness with the device that one received from VirginMedia.
Now the O2 Wireless Box II is leasing a static IP from the Netgear (with DHCP turned off) and all DHCP addresses are now leased from the Thomson router instead.
However, a few questions remain:
1. Thomson: Home > Home Network > Interfaces > LAN_private DHCP Pool LAN_private > Configure parameters for your DHCP pool the > Pool Configuration one can choose the "interface". One of the options is "local network", another two are O2-specific options and a fourth is "Loop".
What means loop and what is its function?
2. There is another choice in this menu: One can assign the IP of a "server", O2 default 10.0.0.138. Assume this is the O2 server when used with O2. Is it dead when not used with O2 or should one assign it to the VirginMedia server (as set in the Netgear). Setting this in both devices might mess it up, so haven't played with it yet.
3. Gateway as set in the Thomson box is 192.168.0.254 and I can connect to the router via this one. However, the standard gateway given to the devices is 192.168.0.1 the gateway assigned to the Netgear. Confuses me a bit but should I really try to change it or is this the correct/best configuration?
4. On top of that strangely I sometimes get 18.104.22.168 as a default gateway which takes me to the Thomson box as well as 192.168.0.254 does. 22.214.171.124 however cannot be found in any of the setting of both devices. Where does this come from??
Any thought would be appreaciated.