Cheers timetraveller.
It definitely is the original Miller setup with the old fashioned voltage regulator.
If we can not get any output from the dynamo then we may need to go for the Alton 12v system.
Neither of us are used to working on a Vincent, but the owner of the bike is now a retired mechanic who had his own business for 40 years and can turn his hand to anything - one of the reasons he bought the bike was to mess around with it
Any trick on how to test the dynamo - think we have ran out !