dont forget its dark at around 4pm in mid winter! how do you work in the dark? 
With my "AFTER DARK" guarantee I work anytime I like. Here's a copy. I am currently posting them through my custy's doors.
Dear Custy,
As you know we strive to keep to schedule and arrive on the same day every month. This means your panes and frames are kept spotless and are the envy of the neighbourhood. You will already be familiar with our RAIN guarantee.
As the nights will be drawing in after October 31st we wish to remind you of our "AFTER DARK" guarantee which works thus:-
Our staff are kitted out with a headtorch which switches on automatically as the ambient light reduces and which is brighter than a beam from a light house. This means we can clean into the corners and do the frames as we always do.
In the rare event you are convinced we have "missed a bit" then please inform us within 24 hours and we will gladly come back in the daylight and rectify the problem to your complete satisfaction.
