My neighbour says he saw what he thought was a magneto amongst the accumulated bits and pieces (Charlie (deceased) was into classic bikes, classic cars, boats & building renovation, but doesn't appear to have completed any restorations - there were heaps of unknown parts everywhere). He will have another look today.
Yes, there is a dipstick under the motor and there is oil in it. I wondered if it was a side-valve but the exhaust 'huffs' on every revolution so I guess its a two-stroke. I assumed the dipstick was therefore for the gearbox (?).
There are youtube clips on the internet showing restored examples running and very nice they are too.
I'd love it, but its a hobby too far at the moment
My avatar shows the late Len Rich in 1970 with the bike I now have - a 1958 Ariel VH