Sorry, but whilst the situation is not helpful, I really don't think this is worth the fuss you made about it. Is it really such a big deal not to be sitting with your OH for a few hours if there is no choice.

(You have not named any medical reasons etc, so I am assuming this is not the case).

A flight was cancelled - BA did their best to accommodate your request, and in the end it all worked out. So well done to BA and also to the PAX who was kind enough to swap seats. A lot wouldn't.