Thanks all, the advice has been great.
Right, I have a spark. And my hangover from celebrating the fact has almost worn off.
So, I decided to make a test light as it seemed easier to see if voltage was present with an 'on or off' indicator rather than the multimeter which, as I had explained, showed a fluctuating reading with the wire I took to be the main supply.
The test light worked well across obvious circuits like the battery but was as dead as a Dodo on my supply wire. That got me thinking there must be another somewhere. So I dug around and found two wires, linked together, hidden under part of the bodywork above the grille. One is pink, the other yellow and they're wound together at the open end. The test light showed they had a power supply so with that wire connected to +ve on the coil and my spark tester in position, I cranked her up and got that elusive spark. My 'whoop' could probably have been heard in Outer Mongolia.
I have read somewhere that the pink wire is actually the ballast resistor. Is that right? My Spit has a plastic unit for that.
Also I think I also read somewhere that with electronic ignition I'd be better off WITHOUT the ballast resistor. Is that also the case? And if so how do I go about replacing it? I mean what makes a wire a ballast resistor and not just a wire?
Thanks!
Edited by Steve Tattersall, 15 January 2021 - 08:51 PM.