As for how to reduce the freezing issue........
Until the 5 Trophy arrives next week, my Renault Megane and Renault Trafic are using neat Halfords "-20 concentrated screenwash" plus 0.5lt of meths in their 4.5lt washer tanks. No problems in Shropshire last Thursday when it was down to -11 degC.
Just to add that the neat Halfords -20 failed to stop the jets freezing when it was an indicated -8 degC, hence the addition of meths. Downside is that the cabin can be a bit smelly, nothing you can't cope with but a small price to pay for clear vision.