Steve,

Ther's a guy called Colin Makenzie, who makes little circuit boards for servos which can replace the analog ones, it uses I2C and read tell the servo what position to move to, and how quickly to do it. It uses I2C to talk to the servos, and also has feedback on how much force is being exterted on the servo (so I could tell if the leg was hitting an obstacle)

He sent me the source code and a circuit diagram, but I don't have the facilites to make circuit boards, and due to a new arrival in the family shortly, I'm not allowed to buy anything, unless it's prams :-(

His website is here:-

http://www.colinmackenzie.net/

Chris