Lego has an extensive support site for Mindstorms, and here is their London Mindstorms HQ.
Want to see a NXT play football? See it in action on the Mindstorms Movies page! Okay, maybe that's a bit far-fetched, but it looks like a really cool bot.
Want to buy one? It's in the Lego Shop but not for the UK apparently. Not to worry, here it is at Amazon UK for £170 (May 2009).
Oh, did I mention that it comes with USB and Bluetooth support? Program the NXT from your PC, and download the instructions to make it do exactly what you tell it!