JA
Quatermass, which also started on that opening night back, had been planned for September, and was filmed in late 1978.
As for 3-2-1, Wikipedia says that it's second series aired from 24 October 1979 to 5 April 1980, but only had 14 episodes. That doesn't add up - it would only take them to 23 January, based on one episode airing each week. So clearly they didn't burn that off as post-strike filler, and actually stopped airing it for a couple of months at some point mid-run.
As for 3-2-1, Wikipedia says that it's second series aired from 24 October 1979 to 5 April 1980, but only had 14 episodes. That doesn't add up - it would only take them to 23 January, based on one episode airing each week. So clearly they didn't burn that off as post-strike filler, and actually stopped airing it for a couple of months at some point mid-run.