Hi there,
Firstly many thanks to all of you who responded with help.
The story so far. Oil was getting into the primary chain case, and getting onto the dry Newby Belt drive conversion.
The considered opinion was that oil was coming from the crankshaft main bearing oil seal.
So I set about removing the clutch, only to find the drive pulley nut too hard to remove. So I purchased a Clarke CEW1000 impact wrench for £55, brilliant off in 5 seconds! What a tool.
I have attached photos of what I found which I hope explains the issue visually. The spacer between the crank pinion and the drive pully is too small in diameter (4mm) to purchase against the oil seal, and hence there's nothing to stop oil from the main bearing entering the crankcase, and in flung all over the drive pully.
I will therefore send details to Bob Newby, and see if the previous owner of the bike had been sent and then fitted the wrong spacer.
I will keep you informed as to progress
Bob Beard