Patching Ceiling

g'day all

i am planning a kitchen renovation soon and need to knock down a brick pantry and oven stack.

i am going to have a hole left in the ceiling and plan to cut the ceiling back square off the wall so i can fit a rectangle sheet in.

my ceiling is made of the plasterglass. i am wondering do i need to patch it with the same or is plasterboard the same thickness?
whats the chances of the same cornice still being available?

house is about 25 years old.

thanks
rap

Generally cornice styles hang around for years, (no pun intended) we built approx 25 years ago and in hunting out a piece for a reno found that all styles in this place still exist. Even if not freely available they can still usually be recast to order as the moulds are seldom thrown out. Generally I would stick with like and stay with the plasterglass, however you can get away with the board, the taped joins cover the gaps and you should get away with thickness.