Wasn't there also a strike in the early 1980s, when BBC1 was off air all day? I'm sure as a kid I saw a yellow on blue caption with music being played, and it was on all day.
I can't recall a strike in the early 80s that blacked out BBC One for the entire day. I do recall the one in 1984 though that did just that - the caption shown that day is shown on this page:
The caption was accompanied by back-to-back Ceefax-in-vision music, all day. Although there were live programmes planned that day, I remember thinking at the time that it was a tad incredible that they couldn't manage some sort of limited service. I can't recall if Ceefax was affected that day - if not, it would've been better to put out 'Pages from Ceefax' than leaving up that caption.
Very different times. They didn't have a huge stockpile of 'Homes under the Hammer' and 'Bargain Hunt' to fall back on!