re-wired a flat a while ago, all the wall lights (about 10 off) were cabled in clear bell wire with panel pins to secure it to the wall - worked for about 40 years with no issues :^O .
Found some DNO submains in a block of flats a couple of years ago. Looked like double covered tails with a 1" wide web between the cores and held back with BFO nails tw@ed through the web. Obviously I took a pick, obviously I cannot find it!