I have plasterboarded my ceiling with the 4 or 5 mm stuff. It is
screwed onto battons I had attached to the existing ceiling. It is
fine in most places, however at its worst parts you can push it in and
it bends in. Will I need to redo the whole thing with the thicker
plasterboard? Or will the skim coat a plasterer will apply be OK? The
ceiling is fairly high and in a bedroom so I dont expect many people
to be pushing and prodding it.

Thanks in advance

James