Yeah but.. you could sort these issues fairly easily.
Loosen the handbrake off inside the car and unclip the end of the cables off each caliper. Take the cables off the car and leave them hanging in the airing cupboard or somwhere warm for a few hours (catch the water that drips out with an old towel, rather than your missus' best linen
When they're completely dry (it'll probably take a couple of days by "air".. so you might want to warm them up with a hair dryer etc.) then spray some WD40 down them and work it out the other end. Then pack a load of LM grease into the cable from the caliper end. You'll have to cram it in.. as much as you can. Heat it with the hair dryer again to help it "flow" down the cable.
When you've stuffed half a tin of grease in there, the beast is lubed. Put back as much of the rubber gaitor that remains..
Refit the cables and tighten up at the handbrake.. and Robert's your mother's brother for a couple of years.
For best results, do it in the autumn, before the cold snap begins and so less time for water to get into the cables (as it will again, eventually).
The door locks is just laziness on your part, I'm afraid...
Spray WD in there to lube them up.. but the kerosene will evaporate (which is why you keep having to do it probably) so you also need grease in there. Pack the locks with grease.. and work it well in. Pack in as much as you can to physically prevent water getting in then freezing.
Also grease the jaws of the lock mechanism itself (where it clamps onto the striker plate) and then work it in by opening/closing the door till it feels smoooother than me in a smoking jacket...
Use graphite (green) grease for the lock jaw.. LM grease (tan) for the lock mechanism itself.
You can also wipe the door rubbers with your favourite tyre shine product, since it contains oils that are rubber-friendly and will prevent moisture freezing the door itself shut..