So, after asking around about my new internet situation, i was informed that there was no way for me to set it up as i wanted to. I had to have my WRT54G as the slave and the new neatgear WGR614 as my master device. With that in mind, i reattached the netgear to my new NTL broadband and put the WRT54G back to it's old position beside the two wired computers.
Just in case anyone else needs to do something like this, this is how you create a wireless bridge between two routers:
1) A router which supports the 'Client' mode. In my case, a linksys WRT54G with the openwrt firmware, the 'slave' router.
2) Any other wireless router, the 'master' router.
1) Connect it to your internet box (be it an ADSL modem or whatever).
2) Set up the wireless connection as per normal.
3) Enable uPnP and DHCP as required.
This router will accept all wireless connections, and can also accept wired connections via it's LAN ports as per usual. All port forwarding should be done via this router.
1) Connect any wired computers to LAN ports on the router. Make sure nothing is connected to the WAN port. You won't be using this.
2) Set the wireless to use the same SSID (network name) and frequency as the master router.
3) Set the wireless connection to use 'Client' mode. In the case of openwrt, the correct mode is called 'Client (bridged)'. In this mode, the router will look for the wireless network with the SSID you specified and connect to it like a regular laptop.
4) Disable uPnP and DHCP on this router.
Note: The slave router cannot accept wireless connections anymore. It can only forward wired computers to your master router.
With that done, my two desktops remain in the same old room as always and connect wirelessly to my master router, thus giving them access to the net and having them accessible to the wireless clients.
The only problem is that the new router is a bit limited in it's configuration and so will end up being replaced in the near future. For the moment, it does the job fine.