Ta for that dp, hadn't come across it so far. Now bookmarked.
Good news is I have managed to get all I need from Draganfly and Goffy, have managed to remake the through bolts that hold things together in such a way that the head and barrel can be attached properly without butchering spanners, and it will shortly be on the road. About a week I reckon. Piston that was in it was in fact from a 350 Ariel (which runs without an oil control ring), and getting sorted has involved replacing the little end along with the piston. Surprisingly thin-walled bush, I thought as I reamed it in this morning. The leccy bits are easy, as it has a later 2 wire alternator - just needed a regulator/rectifier, now fitted. Makes a nice change from my normal diet of AMC twins and the A10.
One of the joys of being in France is that the paperwork is quite easy for old bikes, especially if they come from the EU, and for I think a total of about 100 Euros I've got the papers in order and a French registration doc. Insurance will be less than ten quid for the basics. So a few quid on bits to get it right in the oily department, a few quid for the bureaucrats, and off we go.. Fingers crossed!