Just to confirm I experienced exactly the same issues as you last night, about 10 days of it working and then lost channels again last night. As you say it must be linked to the low temperature.
But as this problem has been on going for two winters now I am starting to doubt we'll ever get year round Sky television at Rainbow Quay.
I'm not sure what the relevance of 15% is or even Sky Q if we can't even get the basic Sky television working.
Sorry for the rant but this is now very frustrating but I do live in hope that this will be fixed shortly.