Thanks for the really detailed reply, much appreciated. I think you’re right that there’s been pooling. I suspect water had been running alongside the sides of the skylight above the ceiling and pooling at the section above the upvc doors.
we will try option 3 initially. It could be that the...
Thanks for the reply, the skylight was what the previous owners got installed and kinda looks like they sliced the top off a conservatory.
The water stains seem to be primarily on the outside but there are some black spots of mildew (condensation?) on the inside. I've also taken some pics of...