So i decided to go with the plastic Pierburg one above and finally got around to fitting it today. Seem to work just fine. Fit into the original plastic sender/pump assembly unit as easily as fully metal cased one would have.

As Andrew correctly stated above, it does appear to just be a plastic shell around a metal fuel pump inside. I guess they managed to make the actual pump smaller (not a surprise with modern motors) and so now have a plastic shell around it to give it the same dimensions as the previous version.