I now have unequivocal proof that the channel crossing Bleriot did have a flotation bag fitted to the rear of the fuselage in the place where I have an auxiliary fuel tank fitted, thanks Andrew for the excellent photos.
So, my Bleriot has now changed from the channel crossing Bleriot to another Bleriot XI variant, I don't really feel like messing around trying to remove the fuel tank and replacing it with a flotation bag, too many rigging wires in the way.
Des.