70s scifi concept album

One (or possibly two) thing(s) seem to argue against the extremely limited-local release idea. The first was your belief that it was an import. If it made it all the way to wherever you are from somewhere else, it seems reasonable to assume that it was quite a lot bigger wherever it came from (a reasonable number of artists and bands have defied this trend, of course)

The other more compelling argument is your recollection that this was a one-off by various artists.  Generally anything involving various artists collaborating on a project - particularly if they're from different labels - involves a fair bit of hoo-ha and usually a noticeable degree of investment and promotion. This wouldn't apply, for example, if it were simply a compilation of unknown garage bands from Akron, but a bunch of presumably contracted musicians from the 70's collaborating on a SF concept album doesn't sound like the sort of thing that would only be released/promoted in Cleveland or Leeds.

This obscurity might be explicable if it were promoted only in its native country, and its native country was somewhere unlikely to make it into widespread English language distribution (e.g. there were enough prog artists in Czechoslovakia in the early 80's to pitch something like this together) - but I think you said you thought it was likely British.

This is where something doesn't seem to gel for me.  Of course, there might be something nobody's thinking of. There were some heavily promoted projects by various very famous artists in the late 70's which are pretty much forgotten now. Some of you might still experience a reflexive wince if I mention 1978's 'Sgt Peppers Lonely Hearts Club Band' - a movie/project which was so loathed that I believe there has been an effort on the part of the collective consciousness to suppress any memory of its existence, despite its throwing together the Bee Gees, Alice cooper, Peter Frampton, and with George Martin as musical producer.

 And when was the last time anyone reading this thought of 'All This and World War II' (1976), which threw together Peter Gabriel, Roy Wood, Elton John, The Bee Gees (again), Bryan Ferry, Jeff Lynne and God knows who else (though I'm not sure how much actual collaboration was going on).

True these are movies, which is why I asked earlier whether it was possible this could be a soundtrack album.

I seem to have made two slightly contradictory arguments:  that ornate and large collaborations between various artists for a one-off project tend not to be hometown affairs, but that they can also quickly be relegated to obscurity by virtue of never achieving either popular or cult success.