OK, I know I am answering my own post, but I thought I would let you all know how unlucky one person can be.
I collected the alternator today, came home and fitted the thing in the rain. Started the engine, nothing. No charge light when the ignition was on, no rev counter and the same voltage at the batteries when the engine is running as when its not.
Also, the two wires fitted for the advanced regulator show the same voltage, that of the batteries.
I think I may have a duff alternator.
I will let you know once this is sorted what it was.