How cold is too cold?

[Scrubsy]

I've tried screenwash but it just doesn't have enough slip for me and if you add window cleaning solution or washing up liquid to it to get some glide it then freezes on the glass.

I'm sure I saw a post on facebook somewhere about screen wash, but they said it's quite poisonous for plants and animals etc so I never tried it. I agree it's usually conservatories that cause the most problems with freezing. On a standard house you'd probably be ok.