[PPuxley]

Thanks, guys. Just come back to read this. I did get it working on the horizontal cylinder but it was a bit hit and miss with me holding the clip thing twisted against the lead. But not on the vertical.
I did try a piece of plain copper wire interposed into the lead, the bike ran fine but it still didn't get the strobe to flash.
Interestingly the Gunson generic instructions say , if you can't get the strobe to flash , turn up the sensitivity. This model has no sensitivity control.
So I think its all just a bit marginal in this application.
Thanks for the offer of a lend, but im going to persevere and try and find a model that will work