Dear Pete, Since you never say that you checked to see if the ceiling and walls are square and not out of alignment, may I suggest that you find the middle of the ceiling and work from left to right on both sides as this will then distribute any foul ups you can make. It make take a while to do this but if the ceiling is not a perfect square (as most ceilings are not) then as a tip it might be wise to measure the width of the room, then using the middle as a starting point working from left to right ;or whatever you prefer to do. It might help you to "size up" (prepare the surface using wall paper paste) using a roller but not too much and obviously a good soft broom to help you put up ceiling paper. Good luck mate.
Anthony Tovey
September 2010