Shame you could not have got the bike to the Douglas Rally at Stow on the Wold today. There was a field full of highly knowlegable people and machines including EW.
You would have had plenty of help and opinions, along with listening to other bikes to see if your noise is peculiar. All in sunshine
There are a good few experts in the West Country (the bikes came from there) but a few are still out on the road from the meet.
Malcolm Meinertzhagen is very good to talk to along with Chris Wright, although neither are in the West Country.
Can not volunteer anyone for the job, but your best bet is via the club. I am sure they will come forward.
Have you stripped the engine to check the crank before running?
They can be a weak spot depending on oiling system etc.
Had to have my B29 crank redone. Worth it though. Heart of the engine. Getting pricey to have done now.
Good luck
Tom