Hello Howard,
Twelve parts, it started off every other issue but went a bit dicky at the end!
ME: 4539, 4541, 4543, 4545, 4547, 4549, 4551, 4553, 4555, 4557, 4561, 4568.
Some pictures and a video of Southam in action on the Nottingham club's track are here: http://www.stubmandrel.co.uk/model-engineering/127-southam-electric-shunter
If you have any questions, just shout.
Neil