We had another of our hardware hacking group meetings last night. Plenty of great discussion, a lot of it focused on the HullPixelBot. Robin had assembled one and added some sensors that allowed it to chase light. Which mostly worked. We're planning a "bot assembly" evening on the 16th of June. I'm going to print out a bunch of chassis and anyone who fancies a bot of their own can come along and build it with us. Then we'll try to get them all going. You can find the build instructions on the Hull PixelBot microsite here. They include how to get all the part's you'll need. It shouldn't cost you more than ten pounds or so.
We also have a Google group about matters Hull PixelBot. If you want the details ping me a message (or add a comment) and I'll get you registered.