[STUART_T]

Just to follow up, I managed to fix the charging problem, it turns out that I did have an alternator that was internally regulated, (dismantled the old one and checked the parts). I ended up disconnecting the wire orginally fed to the alt bat+ terminal (painless wiring) and ran a new wire from the Alt to the fusible link. I also added a resistor across each leg of the warning light which will allow the alt to obtain a excitor even if the globe blows. Adjusted the fan belt to the correct tension just in case (it was a bit loose).

Started the car straight away 14.5v, lights and fan on drops to 13.5v and when the engine revs the voltage raises, all good.

But, when I went to turn the car off it kept running, (needed to disconnect the wire for the idiot light to stop, not a practical way to stop the engine) so I added a diode (from the alternator I dismantled) to the excitor wire and it now stops power being back fed to the ignition and the motor turns off no problem.

Thanks to everyone for your help and suggestions.