... don't come to London ... average speeds of 4.8 kbps (yes that's 4800 bits per second) download and about 3k6 bps upload.It may help to try an external antenna. I got an omnidirectional one for $30. Or you could try a more expensive directional one to try and get to a less congested cell tower.
It's actually faster to get on a tube ... and deliver your message personally ...
However, given the density of network users in London, you might be better off with something like Fon, which allows you to share others wired broadband connection via WiFi. This might make a useful supplement to the NBN. The idea is that the householder shares part of their WiFi with the neighbours and visitors.
The Fon hardware uses Linux and has provision for user enhancements. It might be interesting to have this type of system supplement the NBN.