Plastering the ceiling? So a chunk of the plastering on my kitchen ceiling has collapsed...

So a chunk of the plastering on my kitchen ceiling has collapsed (bath overflowed contained by the room above). Theres a hole say 2 meters by 2 wide open. The current plastering doesnt look like plasterboard and its give a hand up by plaster which has be pushed shrough lots of cracks in small planks above it.

what materials will i inevitability to fix this?
Answers:    this is traditional plastering, must be quite an aged house where they plastered onto battoning instead of out more modern style of plastering bricks, blocks or plasterboard.

i would really recomend getting a professional in to look at this as it sounds resembling some more may come down if you have have a water bleed, plus its not that easy to do if you dont own a clue what you are doing.
thats called lath plastering what you see you can get hold of a stanley knife cut support to nearest joists next put plasterboard in and plaster or achieve thistle bonding and apply thickly to stratum of ceiling then skim over near a finish plaster