The butt joints are fully supported so there shouldn't be significant steps. You could use screws every 200mm at butt joints instead of 300mm elsewhere. I think you are supposed to feather the filler out to about 300mm either side of the butt joint and sand it smooth (hard work and dusty if you use too much filler
). For small filler jobs, I like to scrape with the edge of a steel rule in different directions to get a flat surface. Pay most attention near lights and windows. Use an inspection lamp near the surface to reveal imperfections. Then they should be practically invisible. The change in texture between face paper and filler can be noticeable if you don't prime with a roller. If you are still not satisfied, you can try a heavy lining paper.If you can find a reliable plasterer, it will be quicker and easier for you to get it skimmed. Also let them tape the joints. For large commercial jobs I have heard of rates of £3/sqm for skimming. Expect to pay more for a single ceiling. If you have a lot of ceilings to do, it might be worth going on a short course and learn to skim plaster yourself. It's supposed to be quite easy.
