I had a roof leak; the first roofer inspecting the problem replaced some chipped tiles and also replaced a missing dry verge (which was not related to the leak problem). However, the leak was still there, and had become an emergency, so I e-mailed the roofer with pictures documenting the problem and asked for further action. No answer, so I hired another roofer to re-tile the roof from scratch, and the leak was solved.
After two weeks or so the first roofer replied, I told him the problem was fixed despite his unresponsiveness. He charged me for his part (fair enough), but he also included the material and labor for replacing the dry verge, which wasn't part of the problem, and which was made completely useless since in the end everything, including the dry verges, was replaced. Additionally, I never asked him to fix the missing dry verge (exactly because I wasn't sure whether the old tiling would have been there after fixing the main problem).
It is not a big amount of money (under 150 gbp); however, this situation bothers me: should I try to argue with the roofer or that's not worth the hassle?