Hi chums, hope you’re all well. Started what I hope is a small DIY Damp Fix. Took out and reseated a roof sky-light. The ceiling boards around it are spongy so I’m planning to replace. I expected to find, going upwards, the ceiling board, then insulation and then the metal roof. The Insulation seems to be polystyrene blocks (crumbly in parts) and above that is some sort of lining before the roof. Some of this lining is very damp - looks like some very thin ply. I’m guessing water got through the sealant and under the metal roof but then has settled on the lining (guessing the polystyrene kept it there for a while) before getting through in a couple of areas and softening the ceiling. Does that sound reasonable? My major worrying is that what I think Is lining is actually an old ceiling and a previous owner has simply fixed a leak and then put in a block of polystyrene and a new lower ceiling. Rationale tells me that’s unlikely as they’d have gone to a lot of extra work lowering lights/cupboards too! Any thoughts?