I have replaced both the dynamo and coil on the car now and everything is working perfectly. The idiot light now goes off when the engine is on, showing that the dynamo is charging the battery. The rev counter is also reading correctly.
Whilst replacing them I took out the whole of the fan shroud to make it a little easier to work on outside of such a confined space. This also gave me the added benefit of being able to touch-up the fan shroud that had some paint damage from installing the body a couple of years ago.
PICTURE TO FOLLOW…