none wrote:

The room isnt that big - big enough for an adult single bed and a small
table & storage cupboard.

Just pull it down and replace it.


Would it be expensive to have the ceiling
replaced?

Not particularly.


Are there certain materials that shoudl be used when
replacing the ceiling? I seem to remember people mentioning two
different thicknesses of ceiling board and only the thicker sort is any
good whereas the thinner board will just bow.

Plasterboard, either 9.5 or 12mm will do. Then get it skimmed - it'll
take a good plasterer a couple of hours to skim a ceiling that size.


--
Grunff