Met up with Jody tonight and basically Its running on only one cylinder.
Checked fuel feeds, breather pipe etc all looked OK not pinched etc.
As one pipe was hot we traced the cold non runner to the horizontal cylinder - removed spark plug which was black & sooty.
Cleaned it all up & replaced but still a non-runner so I guess it is electrical unless one of you guys has any other ideas.
Reached the limit of my limited mechanical expertise I'm afraid.
I suggested Jody speaks to Pegasus in Reading to see if they can sort it. Does anyone know of a mobile service that would go to him? He lives north of Maidenhead.