Hurrah!
wey and I are back in wireless mode! We are the proud owners of a new router. Wired in, set up, all ok! When I took the network cable out to test the wireless I was frustrated to see that the internet had vanished, even though I could still see the router. Checking the troubleshooting guide was no help (I clicked past all the silly questions about is it plugged in).
After a bit more faffing, I noticed that the network cable was still connected, and I had in fact disconnected the phone line. No wonder the internet was not working!
Still, I blame Microsoft.