Thanks for your help guys - solved.

Gilly, you were very close.

Pulled the distributor off, and all looked fine - except for condensation.

Wiped clean, reinstalled, fired first time. Lots of smoke initially from extended cranking though, and starting fluid, etc, etc !!

Can anyone tell me if there is meant to be some kind of seal where the distributor mates to the front of the engine??

Just for kicks, tested the CPS - round about 850 Ohms cold.