Since you are one to appreciate simplicity, even elegance of expression...
Thank you. I’m a long-time fan of Miss Manners - since high school. I had no idea she was still alive.
I just went through a round of this while explaining to several offspring why I was buying a flower arrangement for the used-car dealer who arranged and paid for repairs to our brand-new-to-us used car, when he was under no legal obligation to do anything. "A major service like this requires acknowledgment over-and-above a hand-written, vociferously-grateful thank-you note."
"Wow," said various offspring.
The note (in Spanish) will go to Manuel-the-Mechanic. I made sure I had the address of his place of business.