Thanks for your help!
Downloading CNCNET onto my pc did nothing, but adding it to his has put both of our names in the Players box on both computers.
However, I'm now stuck on the next step. When I click the "New" button in the bottom right of the screen, my name disappears from the players list, but no game is created in the lobby for him to join. Again its probably something simple that I'm missing but its fair to say I'm getting a little frustrated.
I'm desperately trying to avoid playing over the internet since the connection we have here means lag is almost inevitable...