Its a bit of a long shot - but does anyone know of a company who can
supply
this? PlumbWorld can't.

Phone them to make sure. They totally changed their listing of
Worcester-Bosch flues when I pointed out they were stocking the wrong parts.
Given the excellent response they gave to me over the phone, I wouldn't be
surprised if they could get hold of it for you. Obviously, mileage may vary.

Christian.