text: In the editor, with bing aerial view in the background, I can see several connected but separately roofed buildings spanning right back to Sidney Avenue. I'm guessing that these are all owned by the church, with some of them being used for other purposes.
  
  The building currently shown on osm doesn't align particularly well to any of them, so I'd suggest you start by editing that to represent the part that you think is occupied by the church, using the roofs in bing to help get the alignment correct. Then create similar areas for any parts of the building used exclusively for a particular purpose, and name them accordingly. Finally create buildings for the shared areas and use nodes to represent them. And if you need any help, please ask :)