Thanks to everyone for the suggestions!

(I was wondering what took Luis so long, but obviously there was a lot to type) ;)

Re retractionwatch - the original paper isn't factually false so much as to need retraction, just pointless.

Re original journal - well, that's what we tried, but there's a wall of arrogance and incompetence that prevents it. (Actually, quite a striking example of the Dunning-Kruger effect, https://en.wikipedia.org/wiki/Dunning%E2...)

Again, thanks to all, and I'll post a pointer here when we move ahead with whatever turns out to be the most appropriate option.

TR