Tiled lean too, condensation

[skell63]

My entrance porch stairs to first floor flat has a condensation problem. Condensation mould at top of wall, ceiling on outside facing wall. Brick cavity wall, insulated with injected polystyrene beads, roof insulated with fibreglass quilt. There is an electric convector on ground floor, walls and ceiling were lined with 3mm insulated wallpaper 2 years ago. walls have cross vents. Top of stairs I have a curtain to prevent warm air being lost. Convector heater on at 12 degrees C. To touch touch ceiling is cooler than walls. What's best insulate roof taking tiles off ( Not my roof but landlords - Council - permissions) or fix battens inside, fix insulated plaster board, skim. or expanded insulation board dot and dab, and plasterboard, skim. Your thought suggestions. Thank you

 

[Wayners]

Is it open to stairs?
Lack of air movement probably.
Areas like that could go mouldy from condensation dumping on the cold spots.
When I wallpapered or painted areas like that it needed a fan to dry it, or it would stay wet for weeks and go mouldy.
No amount of insulation will help as it gets to a point where adding more insulation don't do nothing.
A summer fan on a timer blowing up the stairs will help circulate air. See how that works out.
Maybe 20mins 3 times a day will help circulate the air enough. Run your own experiment creating air movement.