I’m following this with interest. There is no real equivalent to O Gauge Hi-rail in UK, although the O Gauge Group I went to a couple of weeks ago might be so defined.
There WAS once a definite school of “3 rail scale OO” at one time, using 3 rail and stud contact track in a scale modelling context (including stud contact EM at times) mostly with hand laid track.
I think it’s mostly because Tri-Ang, who out-competed Hornby Dublo, were always 2-rail so the “nostalgia” sector here is “Tri-Ang 2-rail”