Well I obviously still don't understand insulation and this is causing damp problems along the edges. Our roof is made of aluminium (no leaks) there is a gap between the roof and polystyrene sheets (but only because that's how it hangs so to speak) then plywood.
Where the wood burner flue goes through, there is roughly a foot square of space with no plywood or insulation, so straight to metal.....some mornings, there is condensation collected on this bare metal (esp when wood burner gone out and all windows shut)
I wonder if it is this water condensation that is collecting there, running along and causing the dampness along the edges.
This is all a learning curve, we thought we sorted it but nope so will do it again when it warms up.
What do you do on your ceilings? what do you do around the flue? any thoughts ideas much appreciated. 3rd time lucky eh?