The message
from "Phil Anthropist" contains these words:

If they are on the kitchen ceiling a surveyor is likely to say that
they are
not permitted due to problems if there is a kitchen fire.

Having had a fire in a kitchen in which polystyrene ceiling tiles were
fitted I can only strongly advise you to get rid of them at once. They
made a small fire very nasty indeed.

--
Skipweasel
Pay no attention to that man behind the curtain.