Package from Maplin arrived and I waited until the afternoon before venturing out and trying the resistor. Started with the 0.6W as I don't remember anything more substantial being fitted to the old cars ignition switch.
Resistor temporarily spliced into the ECU line and the car starts! Unfortunately it "idles" at around 6000rpm which is a little noisy. Brief investigation reveals that the idle screw adjuster (plastic twisty knob) was twisted quite a way in. Adjusted to a more reasonable level and we have a good idle. Left it to warm up for about 10 minutes and all's well with no leaks. Couldn't resist it so I gave the throttle (the cable in my hand) a quick blip. Oh yes! This is what it's about :-)) Neighbours duly impressed (I should imagine) I decided to start some more productive work on the car and try to get it finished before the sun disappears for the 9 month winter