Thought I'd mention it in case anyone ends up with bald spots on their door liners which then leak. They're overpriced spare parts and a minor hassle to install but I'm taking the view that prevention is better than cure and all that...
If you look on the top of your door, you'll see that you've got a velvety liner running around the top perimeter closest to the occupant. As one of the seals, it gets wet and is thus prone to freezing. When it does it'll bond like super glue to the car and on opening the door, it'll give at the weakest point which is usually the liner and you'll end up pulling pieces out of it. It looks unsightly and then leaves an open channel for water to flow into exacerbating the problem if bad weather persists and eventually, it looks a bit tatty and needs replacement.
As a precaution against this happening, I've used 3M detailing tape used to mask off areas when polishing, it doesn't leave a residue but I've run a neat line along the inside sill. It's not a strong adhesive so when you open the door, the theory is that this will give before the liner and allow you to open the door without creating bald spots. Granted, it's not the prettiest solution and isn't visible from the outside if done neatly but it's only temporary for when the weather is so inclement. It's worked a treat so far.
Running a cloth along the inside edge when it's thawed a bit to remove excess water is also a good plan.
Hope this helps some of you out.