flaky ceiling, but plaster good

i've just removed the polystyrene ceiling in my house, theres no glue up there just the paint over the plaster has come off in bits all over the ceiling,
what should i do next to get a smooth or lightly textured ceiling?
thanks
matt

Fill & sand all the chipped areas. but you still may not get a completely smooth ceiling straight away and may need to repeat a few times. Try getting some light shining at an angle on the ceiling, this willl give you a better indication of how well you are doing.

Avoid any emulsion with a sheen to it, this will highlight any irregularities, matt covers a multitude of sins!

Other than that, you are looking at lining paper or even skimming if its really bad