Update:
I've fitted a temporary switch, position 1 connects battery direct to coil (via solenoid) for easy cold starting, position 2 connects ignition to coil for normal running.
The routine is, switch in position 1, start engine, move switch to position 2, easy.
New solenoid is on order and should be delivered Friday/Saturday so I'll report back when it's fitted.
Thanks again Gordon, much appreciated, price of a pint or two of Larkins on its way to your P.O. Box.