Note the non-standard headlamp, with its apparently lashed-up bulb holder ....and the lack of choice in 6v bulbs I'll probably make something up from a domestic Halogen bulb.
At least the brake/tail light now works!
It turns out that the auto clutch is binding.
Unfortunately the 'nut'/kickstart cog holding the incredibly simple clutch in is an odd, non-standard beastie( see here and here)
It probably only needs a new tyre for the MOT, but until I can make up a tool for the clutch, it'll be out of action.
2-stroke tuning to follow