TNG Episodes on VHS were generally available quite significantly in advance of broadcast in the UK. The BBC broadcast TNG series 1 to 4 about two years behind their original air dates in the US.
Sky (premium satellite in the UK) got first run rights after 1992 for TNG Season 4 onwards but was still usually six months to a year behind the US, and the BBC was often a year behind that.
So I suspect the full unedited version of the episode was indeed available in the UK, probably before the BBC even became aware of the dialogue about Ireland.
I imagine so. The BBC would have had no control over foreign VHS releases.
CIC Video was also the distributor for Star Trek TNG on VHS in the UK, although they weren't imports of the US releases as the UK used the PAL recording system whereas the US used NTSC, which were not compatible, so you couldn't play US tapes through UK TVs, and vice versa. They were almost certainly manufactured in Europe somewhere.
UK law gives the BBFC (British Board of Film Classification) full control over censorship and ratings of pre-recorded video releases (significantly greater legal power than the FCC/MPAA has ever had), indeed to be legally sold here they would need the BBFC rating on the package, and the BBFC can censor sensitive topics in the UK.
However the decision to skip The High Ground was made by the BBC, not the BBFC. It was not a matter of law or even government policy, it was a case of the BBC acting in what it believed was the public interest at the time, as per its mandate as a state funded broadcaster.