"Dear Sir/Madam,
Santa Claus arrived early at our house, your team arrived days before the arranged date and finished on the day they should have started the installation, brilliant.
May I also take this opportunity to say a big thank you to the fitting team, their workmanship is superb, their friendliness towards my family soon broke the ice and we soon became one big happy family. These two lads are a credit to your company and I for one would recommend you and their workmanship to anyone.
Kindest Regards,