Depends on how even the block work is underneath plaster, if it's okay a good plasterer will be able to give you a good finish, if not dot and dab will give good flat walls. But take in to consideration that if a door opening is on the wall it will probally alter the depth of the frame.
Hope some help.
Ask a plasterer. Some will say strip right back and replaster with bonding coat and finish coat. Others will say dry line and skim. The former will probably be more expensive and take a lot, lot longer to dry out for decorating.
However, before you make that decision I would suggest that you need to start finding out if the plaster is completly blown all over (or even if it's just completely shot - turned to dust) or it's just in a few patches. If it's just a few patches then it can probably be patched but if it would start to look like a quilt then start again is probably the best option.
Perhaps the best solution is to get two or three plasterers in to give you on the spot advice and a quote. Can't tell remotely.
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