Dave, (Pristine),
You're in Kent! Think of the poor ginger window cleaners in Scotland and how tough they have it!
You've got nothing to worry about; if they can do it so can you.
The only thing I don't like about the Winter is the shorter daylight hours; I normally never work past 3.00 pm, but sometimes I want to, but in deapest darkest Winter, it starts getting dark around then and working on residential houses in the dark, makes me ponder that my customers may think I'm a bit 'daft'!.
I think the clocks go back this weekend; and that always winds me up (though I know there's a good reason for it).
However I can and have cleaned windows in the dark without complaint.