Problem is the early bay locking system is very heavy to operate and therefore does not lend itself to operation by a small servo/electro magnet. Much easier with later bays that have the traditional button by the window.
I went to road radio a place that fits aftermarket alarms and sound systems if memory serves they quoted me £20 a door for central locking plus the cost of a Clifford alarm to run it. I will get round to doing this once the van is near compleation.
Found what I was looking for: http://forum.earlybay.com/viewtopic.php?f=2&t=2064&p=161447&hilit=central+locking#p161447" onclick="window.open(this.href);return false;
Read through - he used a generic kit from Maplins with no problems (as such)