Car Bodyshop repairs cars park on single yellow lines

I'm not really sure if this is the correct forum to post this in - apologies in advance!
There is a small car body shop opposite my flat. They make a lot of noise during the day/evening. They jack up cars which are parked on single yellow lines in front of the garage and repair them. They use noisy power tools and stretch the cables over the pavement. The noise is a real nuisance esp as I work at home, and I would like to report them for that. Am I more likely to get them on the traffic violation? Repairing cars on a single yellow can't be legal surely, it's not as if the cars have broken down - the garage simply doesn't have room for the volume of trade they are doing.
How should I go about this and what evidence would I need to collect?