I think this is the final episode to come from unusual surroundings. We've had a fair few during the BBC4 run, Peter Powell out of vision (plus DLT
doing the same the previous week, though BBC4 didn't show that one), Simon Bates and Olivia Newton-John in an empty studio, Tommy Vance in front of a CSO backdrop, those several weeks in 1984 with a cut down set. The nearest I can think of post-1988 is the episode from 1994 that had to go out live (at a time when the show never went out live) because of a strike the previous day when it should have been recorded, but it otherwise looked and felt the same as normal.
That's true enough. There are a few live episodes in 1989 which I think were supposed to have been recorded but were broadcast live, in spring 1989 there were a lot of strikes at the Beeb. But as you say, not so's you'd notice.
In fact I'm not sure we've had any live episodes yet in 1988. Certainly in recent years there hasn't been as many as in the early eighties, circa 1983/4 it was probably live more often than that. By the time we got to 1987 it was pretty much only in Bank Holiday weeks (where the chart came out a day later and they lost a day's preparation) when it was live, and now the chart is published on Sundays, even that's not a problem (and I think the recording day has now moved to Tuesdays rather than Wednesdays). Of course, there is a live episode to come in a few weeks, with disastrous consequences.
Of course, way, way in the future, a few weeks before it ended for good in 2006, there was an episode hosted by Rufus Hound and Annie Mac at T In The Park made up of repeats and clips from the coverage, although that wasn't for any technical reasons, the show was just staggering to a close and it was a way of making a cheap episode. Of course in that era one show a month would be recorded in the same session as the previous week's episode in any case.