I had been considering painting the ceiling with a couple of layers of liquid damp proofing before applying the last ceiling layer and I had kind of been putting off adding the layer for this reason. There was some concern that moisture might seep up into the ceiling void along with the remote possibility of a roof leak. Having this layer would perhaps alleviate any damage that may result. Anyway, instead thinking about it too much, and bearing in mind that there is no real downside to doing it I thought I would just go ahead with it. So that was it, I painted two coats of this over the weekend; one on Saturday and the second on Sunday. I can now move on, and next weekend hopefully finish the drywall once and for all!!