Two days ago in the morning it tool quite a force to open the drivers door due to being iced up.
Got the door open, but the handle stuck about an inch out (at full travel ) therefore the door would not latch closed, I eventually pushed the door and handle closed and locked the door closed using the hey blade, ( nearly broke the key, it was so stiff ) the central locking no longer worked. It appeared that the latch mechanism in the handle was frozen. Got my grand daughter to school, got home and left the car running to warm thru for 30 minutes then eventually the door pull handle worked.
So besides using a silicone spray for the door seals, I injected the same into the latch mechanism, now back to normal.
I then did the same for all door latches and they are all now noticeably smoother to operate. lesson now learnt that it is not just the door seals that get iced up

I just used to wee a bit on my Jag door lock when it froze. You have to be quick though when it's that cold ! It did work though.  RR owner