I've tried halfords neat screen wash the pink stuff, used it neat with a bit of water, havent tried it in the very cold weather, but overspray on the paint dried like a crystal and was hard to wash off... i.e. saw some dark likes where the water had been, polished out easy but i still stopped using it...
Car plan blue s**t it what i use 50:50, still frozen when i get in the car... but the engine warms it up, its usually the hoses and sprayers frozen in mine not the bottle...
Brand new washer pump has helped as well