Bloody hell - I would not be driving with the snow still on the roof !.BTW - Shouldn't be driving a car with 4" of snow on the roof #illegal
If it’s been sitting there all night, the cold temp transfer through the glass will make the cabin even colder.
Trust me, my previous car had a glass roof and it does take longer to get the cabin toasty.
My present car is the same make and model to the previous car, but it has NO sun roof, much quicker to get the cabin toasty !.
The MG has a FULL piano roof on the Exclusive model, that is a LOT of single layered glass to heat up !.
Just to say also, when it is really cold ( -6 ish ) you will hear the glass roof creak and groan when going over speed bumps etc.
This will stop as soon as the internal temp rises of course.
Note of caution, don’t try tipping opening the front section of the roof for ventilation until the temp has been raised.
Otherwise the roof will stick with the frost to the roof and will rip the wind proof seals around the pano roof.
If you are really unlucky, you even blow the fuse or burn something out by keeping you finger on the button.
I know somebody who did both of the above and the repair bill was huge !.
Given the above, am I having the pano roof - of course.
For me, the Pro’s beat the Con’s hands down.
The light it allows into the car makes it feel a much bigger space than it already is.