456, X Street, Y Avenue
[Subject: Normally bold, summarizes the intention of the letter] -Optional-
Dear ANDREW HALL,
I offer my compliments to your team following my recent visit to the York Service Center. I had no expectations of being able to repair my car cheaply, as other garages had quoted very high figures just to have a look at the problem. One of your mechanics though had a look for no charge, and found that all I needed to do was have a new fuse, something that was again replaced for no charge.
I will be bringing my car to your garage for all future requirements and will recommend the York Service Center to all of my friends and colleagues. A good set of mechanics is a hard thing to find these days, and you should be proud of your team.