I'd like to recommend Jack Hart who plastered two rooms in our house near West Dulwich (main bedroom and sitting room). He boarded up the ceilings, patched big gaps and skimmed plaster all walls and ceiling. He also did some damp proof injection in the sitting room which had a historical damp problem. He's very professional, takes good care of details, clean and tidy and with competitive prices... plus he's a very nice guy too!