Sadly, I missed their call when they phoned to tell me about the extra work. (And no, you don't have to say anything. I know.)
The folks behind the counter were super-friendly and helpful today, though. It was a different crew entirely, and included one of the gentlemen who first drew me to the shop in the first place. The first time I went in, there was a hip active dude who had wracked up the drive-train on his mountain bike badly. The tech asked him what he had done, and he started talking about his weekend adventures in the Fells. The tech interrupted him, asking, "Do you know that it's still April?"
"Yeah," said hip active dude, "So?"
"What you have here is kharmic debt. The Fells are closed to mountain bikes until May 15 for a reason."
I have personally seen the damage that bikers do to the trails in the spring, primarily because the ground is too wet to support the extra wear and tear that the knobbies leave in their wake. Erosion is a problem in any season, but it becomes catastrophic when it happens in the spring. Needless to say, I was pleased to have found someone who was conscientious enough to call a hip active dude on doing something stupid.