Derek wrote:

When I moved into my house in 1975 all the ceilings were done with
polystyrene type materia.It was about the same width as a roll of
wallpaper and must have came in rolls. When you look up at it looks
like all the pieces of a jigsaw puzzle and it is very hard to paint
if ceiling gets dirty from smoke. Does anyone know the name of this
material? I would like to remove it but am afraid to start . Has
anyone ever removed this and is it hard to remove. There is also
polystyrene? coving round the walls as well.

If you can get through the layers of paint, I suspect acetone would
dissolve it, but still leave a mess such that you'd want to get it
skimmed or overboard it with more plasterboard.