One Foot In The Grave was a sitcom my mum and dad went to see recorded when I was only 8, it was for their third series and my mum remembers it well, it was the episode "Monday Morning Will Be Fine".
She said she remembers it being filmed in Studio TC8 at BBC Television Centre, a studio which I would later visit on numerous occasions myself.
She said there was sets which could be moved, for example the view into the kitchen from the Meldrew's living room and the view from the kitchen into living room, they had moveable walls to ensure each area was covered.
The had a specially created fireplace wall which could be moved, when the camera was filming in the kitchen set.
I know Susan Belbin, the producer of One Foot, specifically arranged the sets so it looked like a real house - with, as you say, walls that could be moved - so they could start a scene in the kitchen and it could carry on into the living room and it would look totally natural, as opposed to other sitcoms where you couldn't do that because the two sets would be completely separate.
In Richard Webber's book it talks about how, because of that, it also used more cameras than you would usually have for a sitcom, so they be could placed all over the set. In the book it talks about how, in the episode set in the boarding house, Susan Belbin couldn't direct it as her mother was seriously ill, so Sydney Lotterby stood in, and he was amazed to find they were using nine sets (on two levels) and nine cameras, which was the most he'd ever seen used for a studio sitcom.
Of course, One Foot is I think the only show to actually have a sub-plot about being in a studio audience for a sitcom. "The only highlight was urinating next to Peter Sissons!"
I remember seeing all sorts -The Stand Up Show, Little Britain, Dinnerladies, Never Mind The Buzzcocks. The one that stands out for me was some Gaby Roslin vehicle in TC1, something about celebrity guests talked about something from their past, was a bit dull and because they were doing bits for several episodes, lots of costume changes for Gaby in between items. It lasted so long that when they finally let us out for a loo break several members of the audience just kept on walking and left the building (we did too, but went to the bar!)
If only because I remember you telling that story before, not because I have any fond memories of the series, it was actually Carol Smillie rather than Gaby, and the show was Star Secrets -
https://genome.ch.bbc.co.uk/schedules/bbcone/london/1999-07-05#at-19.00
That's the sort of cheap lightweight pre-watershed show you don't see these days, no great loss.
That always used to be a classic tabloid story, gleefully reporting the audience walking out of unsuccessful shows, I remember them doing that about It's Ulrika, the one-off Ulrika sketch show, which apparently took hours and hours to record. I also remember the Mirror printing pictures of a deserted audience for The Big Ticket, the hugely unsuccessful lottery show, having all apparently legged it several hours into a marathon session. I remember Patrick Kielty was on HIGNFY that week, and they mentioned it and he said it wasn't anything unusual, it was just a quick break and they'd let them go to the toilet. And Ian Hislop said "They'd
all
gone to the toilet?"