Bathroom and dining room reversal

Question

This was part of something I watched on UK television sometime in the 1980s. I can't remember if it's from a film or tv series.

There was an atomic war, however things seemed fairly normal afterwards but an absurdist society developed (I'm not too sure about this bit TBH)

Anyways, what I remember is several people meet up in a nicely decorated room, they all drop trou and sit around (on toilets) a table chatting and having pleasant conversations.

One excuses himself and leaves the room, he goes down a corridor into a tiled room and enters a cubicle. He bolts the door and then sits and eats a meal. Then washes his hands and returns to the party.

Answer 1

I believe that this is an episode from Luis Buñuel's surrealistic comedy "Le Fantôme de la liberté" (The Phantom of Liberty).

From the plot description on Wikipedia we have:

The professor continues, using a dinner party at his friends' house to illustrate a point he is making. We then cut to the 'dinner' party which is being held in a modern bourgeois apartment.

The guests are seated around the table on flushing toilets. They politely discuss various issues around the topic of defecation whilst publicly using the toilets that they are sitting on. When a guest is hungry, he excuses himself and retires to the dining room, a private cubicle, to eat food.

That matches your recollection.

Answer 2

This could be The Bed Sitting Room which is certainly an absurdist comedy in a post-nuclear holocaust environment. Details on IMDB: https://www.imdb.com/title/tt0064074/reference/