The insurance company and probably by now their designated assessor have undeniably crystal clear photos of the stone damage. A window that is not repairable and the only remedy will be to replace it.
As it stands, in addition to paying out the insurance excess, I will now have to, at my expense, take time off work so the assessor can confirm the window damage is exactly as the photos show which in turn will reduce their the repair bill by precisely nowt!!
If the insurance company have an issue with the cost why don't they simply take that up, and come to a financial arrangement, with the dealers who provided the repair quote?