I have a ceiling that, let's say is a bit of a mess, having suffered sagging from past water leaks in a couple of places and having been patched (badly) when previous extension work was done. I was going to cut out and patch the offending areas and then get a reskim, which we are also getting done on all the walls. However, it has occurred to me that it might be better to just clad the entire ceiling in another layer of plasterboard after cutting out the bad areas. The current ceiling is far from flat anyway, even in the "good" areas so this solution would sort this out as well. Are there likely to be any problems with this and is there any advice that I should heed?