Good News!
While carrying out further cleaning/dismantling I had already removed radiator for refurbishing and then took off the side plate that retains the 2 hoses from the water pump. Guess what was nestling wedged between the hoses?-yes that little "brass" spacer tube and, when I had calmed down & finished dancing around the workshop, I discovered that it is magnetic so is only coated to appear like brass-picked the little b*****d out with a magnetic screwdriver. Honestly it couldnt be seen from above or underneath!
So I am going to put it all back together once I have cleaned front of engine & checked any corrosion around oil & coolant pipes.
And YES all the inlet holes are plugged with soft clean rag.
Just had a thought (quite dangerous at my time of life!): How about attaching new inlet rubbers to carbs with the clamps BEFORE offering up carbs to cylinder head?
Am going to change the small bore rubber hoses that link between the carbs as they look past their best & I dont want to remove the carbs again in a hurry!
Thanks for all your replies/suggestions