No new debris in the float chamber, which is good news. Dug out the old float and lever from the original Solex carb. What a work of art compared to the cheap Solex copy. Fitted it to the new carb and all appears to be good.
Sure enough however, there is evidence of a wet gasket just where David had the issue with his copy Solex, so it may well have a similar issue there, and could explain the constant petrol odour. So thanks for the info David.
Norman Anderson