Saw this one a while ago. I'm not a professional tiler by trade but I was amazed that this guy was getting away with it. He was a bathroom fitter and said that he had been fitting bathrooms day in day out for the last 20 years. I don't know him - he saw me mixing plaster, stopped and asked if I would skim a ceiling for him. He told me that it was boarded and ready to go. When I got there I found that it was indeed boarded but that everything else in the room had been done including tiling and grouting. I didn't have any tape with me to stop the plaster bleeding into the grout and he didn't even seem bothered by it! The grout line around the top of the tiles meeting the ceiling varied between 10mm to 18mm. The mitres didn't meet up and were proud, he didn't bother drilling tiles, he just cut them and then pieced them together around the object. He also did all of his own electrics so I suggested that the owners get an electrician in as the downlights were not even bathroom rated