Does anyone dare to make a wild guess?
From which time period do you think this surface layer is?
That is, tiles on the wall and old plastic flooring.
Underneath the old plastic flooring, there was apparently an older tiled floor.
Risk of asbestos in the adhesive and grout, or is it too old to possibly contain it?
Yes, the mixer yes. But they didn't run 22 or 28 pipes to the mixer in the 80s, so the mixer has probably been replaced. Hard to see but it could also be an iron and a copper pipe... then it is at least older.