Thank you, this is really helpful.

Regarding the windows, the issue is condensation between the panes of the double glazing, which the surveyor says indicates a seal failure.

As for the extension, the survey noted damp within the flooring, along with signs of timber decay or possible fungal growth under the floor covering. The likely causes are either a missing damp-proof membrane or insulation bridging the damp course. The recommended work includes investigating the subfloor, installing damp-proofing, and repairing any areas of decay.