I thought I may as well throw a post together about the robots that a few fold from work an I build for the Harwell campus open day.
These were heavily based on the sumo bot design, but I modified them slightly to not rely on a fiction fit joint (or cable ties), I did however keep the cable tie mountings for the servos since they had yet to be delivered when I was redesigning them.
They all used an Arduino and nRF24 radio modules for communication, the control was done through an Arduino powered base node which we had originally planned to have accept commands from three different controllers; one using a web UI, one using a Leap Motion and one using instrument control software. For various reasons (mainly because it was the most reliable) only the web UI was used on the day.
Code and such can be found on GitHub.