The BBC's airings - or lack of airings - of the episode are pretty clear, and I think well known amongst British Trek fans. If you search old usenet posts, you'll see plenty of discussion about it from the time. The BBC's Genome site is easily searchable to find all episode airings.
TNG first aired in the UK on the BBC. But the last time the BBC had the rights to TNG was in 2008, when they ended a weekly late-night re-run of the series from the start. Here's the airdate details of that airing:
But the series had only run three times prior to that. It first ran in 1992 (two years after its first US broadcast which wasn't unusual at the time), and later in 2002 and 2007. In each of those years, its early evening BBC2 broadcasts skipped the episode. You can again find all of this on the Genome website which lists every airdate of every show aired by the BBC.
Plenty of other channels have aired TNG over the years in the UK, although surprisingly, none is doing so right now. But back in the 90s, the episode was released on VHS a few times, when retail tapes were available with first two, and later four episodes per tape. Indeed, checking the dates, it looks like you could buy the VHS of season 3 prior to the BBC actually broadcasting it by several months! You had to rent episodes at Blockbuster, if you didn't want to wait for the BBC airings. And the tapes very much included The High Ground.
While I can't say what Sky did, they ran TNG fairly much non-stop for many years. And while, even post The Good Friday Agreement, there were ongoing concerns about anything destabilising an unsteady peace accord, I'm certain that if the BBC was airing the episode by 2007, then Sky would have started showing the episode too at some point.
These days, in the UK, I can stream the episode happily on either Netflix or Paramount+, or buy the episode at Amazon/Google/Apple/wherever. And the UK Blu Ray boxset remains available for purchase.
So "remains banned" wouldn't be accurate.
Adam