Hi Laker,
Some people still have the old buff and green logbooks that had details of several previous owners written in them. It is possible that the bike you are looking for is out there and the old logbook is with it. If you are prepared to give the names of your father and uncle then B31 owners could have a look.
The logbook would also have the address but I would suggest not giving this but using that information to clarify that any reply is genuine.
Good luck.
Dave.