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Could someone advise a complete novice on the best course of action please. My immediate reaction is to go to somewhere like B & Q and get some repair plaster. However the existing plaster is so very sandy and crumbly and so I'm not sure whether to knock it all off, or whether i can paint it with something that would 'solidify' it? (I've never done any plastering before but have heard that it's not that easy).
Then I thought I would put some Polycell surface filler down before putting emuslsion paint on top of that.
Grateful for any advice simply explained for a novice about the best way to deal with this problem please. Thanks.