conservatory too hot?

depend on plastic, but up around 50C for some plastics to start to deform back to pre injected or pre extruded stresses*.

Not sure but ISTR Land River had some plastic fascias that simply became unusable after been left in sunny car parks. ] And a glass house in the sun CAN get well over 50C.

• I get tubs of things in vac formed plastic from the supermarket. I keep em for freezing stuff in. They will deform with near boiling water.

But EP foam doesn't of course.

Shame it doesn't explicitly refer to "uPVC, conservatory windows for the framing of", but this looks interesting:

Byuckling and depending on the materiel catastrophic failure.

However unless you are going to turn it into a kiln, I'd suspect this would not be an issue. Brian