Plugged the dash in - connected up the umbilical to the tin-top and ........
......... no electrical faults!
Looks like Andy wins a prize!!
I only found two unrelated faults: 1 - I had broken the O/S repeater bulb when fitting the lens. 2- Only one of the twin Air horns works? - air problem rather than electrical.
Here's the evidence:
So now I really should get a battery whilst I can still start the tin-top. Then, with no more need for the umbilical (and if I cobble up a gearstick and get my hands on a Vectra steering wheel) it should be able to move under it's own power for the first time.
Time for a garage tidy up now!