UPDATE - I have now heard back from my customer.
So this is what i emailed to the customer.
"Dear Mr ****,
Many thanks for communicating with me, I am sure that you must be concerned about this matter on your property. Also thankyou for sending over the photo following on from our telephone conversation earlier on 28th March.
First of all I would like to assure you that the methods we use and have used on your property since 2016, along with the specialist brushes selected for your windows, are chosen so that it is not possible to scratch glass of any sort, whether new glass or skylights.
The brushes are made by a specialist company who have been supplying them to the WFP window cleaning industry for over a decade now and are made using PBT polyester bristles and nylon stocks. Both materials are not hard enough to scratch glass in use. They are also designed not to hold on to grit or stones in cleaning.
We do not believe we have caused this scratch due to the high quality tools and standards we use.
However we have found that sometimes scratches have been caused by other work done nearby or general house or garden maintenance and then not noticed for many months or even longer until a bright day when the sun strikes it from a certain angle. Because imperfections may be imperceptible in dull conditions and the window is often dirty due to weather this might go unnoticed until a sunny day after the windows have been cleaned.
Therefore, in view of the above my operative did not cause the scratches to your glass.
Yours Sincerely
Josh"
He Then replied to me 5 days later with the following!
"Good morning Joshua
Good news I have been able to remove the marks on my kitchen window. As it was marked or bruised rather than scratched, I was able to use a mild abrasive polish which did the trick.
Best wishes ****"
Right, so come on then lads. All you lot who told me to just be professional and hand over insurance details and accept liability. Then the rest of you who told me to go inspect in person. 90 Minute drive round trip + fuel.
Looks like i made the right choice. However, how should i proceed now? Kindly tell him to jog on, for accusing me of scratching the glass, and then not even apologising after realising it was marks that would come off? Or should i just carry on as normal and keep cleaning the windows? What would you lot do.