Below are some pictures of one of the drive motors used in Hard Cheese to win series 2.
It is a standard Ford windscreen wiper motor found on Escorts & Fiestas, with some modifications they are quite useful.
The drive shaft has been extended by adding a steel bar with a taped hole at one end to screw on, it is also pinned with a simple pop rivet shaft.
The hub you can see top right is slotted to fit into the webs on a nylon wheel from a DIY store, the wheel was held on with a washer and circlip.
Bottom left shows you where to cut a link that connects the brushes to the case, this must be cut if you want to bolt to a metal chassis.
One last thing to remember is that these motors have a tendency to run slow in one direction.