Finally managed to sort out getting wifi access on the London Underground through my Three account on my phone. You need to set it up above ground, which I did, but didn’t quite get my password right, so when I was down on the tube, it didn’t work the first time. After resetting my password I was able to connect to the underground wifi.
It only really works at the stations on the tube, not in the tunnels. However with the short time between stations you can still do stuff like read web sites, do the Twitter and send e-mail.
What I find it most useful for is tracking train times as I return to Paddington after working in London.