Let me put on my Aspie "Over-thinking cap".
Interesting question given two considerations.
1) Does this long-running soap opera involve
a specific point in time in our relative past as opposed to our relative present? If it is intended to reflect the past, I could see the point of such a question to maintain a sense of social continuity- purely from a creative perspective. Though if the show itself deliberately evolves over time, then it would seem logical to presume that
present moral and legal standards would be highly relevant, "pre-watershed" or not IMO.
2) If heterosexual marriage has never been an issue relative to broadcasting content and viewing time considerations, applying any such limitations to gay weddings might invite legal accusations of discrimination in any legal jurisdiction
where gay marriage is perfectly legal.
Yet in Northern Ireland, same-sex marriage
is still illegal under law. A political issue where
both Catholics and Unionist Protestants continue to block advancement of marriage equality while Sinn Féin supports it.
I can only guess that the BBC routinely broadcasts the show to the six counties of Ulster, where individual episodes may or may not be subject to censorship as opposed to all other jurisdictions of Great Britain where same-sex marriage is perfectly legal. Ironically the Republic of Ireland also constitutes one of those jurisdictions as well and voted for same sex marriage a few years ago.
Under such circumstances, I think it's a fair question of Rich to ask. Can't help but wonder how the BBC may handle such an issue likely relevant only to Northern Ireland which has had its share of "troubles".