I have just moved in to my first house and am starting to get to grips with DIY. Unfortunatley the house is full to the brim with polystyrene ceiling tiles which I am in the process of removing. I have completed removing the tiles from the ceiling of one room and found that the plaster underneath has a number of cracks. Most of the cracks are hairline but around the bay window a large chunk has fallen off about the size of an A5 piece of paper. The cracks around the window are also bigger than elsewhere on the ceiling. My question is, do I need to get a plasterer in to skim the ceiling or can I use a cheaper option such as filling the gaps and using a basecoat? I am worried that the rest of the ceilings in the house will be in similar, or worse, condition could anyone give me an idea of how much skimming costs? There are five rooms in total with the offending tiles all of which are 12ft by 12ft or smaller. Your advice would be greatly appreciated.