Rarely work in urban areas, and haven't tested it for at least ten years, but the rules and regs associated with double yellow lines specify an exemption for those "engaged in the maintenance and installation of water and electricity", or some similar wording.
On one occasion I was working at the end of a local High street, where there was a bus sized double yellow lined lay bye alongside the road. Arrived on the first morning to see the Chippy unloading his van and being hassled by a bad tempered traffic warden, who wouldn't let up until he had moved his van to a car park a hundred yards away. At this point, I pulled into the bay, was totally ignored by the warden, as if I was invisible, and parked there the whole day, and every other day, until the job was finished.
On another occasion, I was working in a very narrow yellow lined street, which also had a small van sized lay bye at one point along it, in which I parked. After a day or two, I encountered, and got into a stand up argument with a prod nosed neighbour over my parking arrangements. I politely told her to foxtrot oscar, and went back to work.
An hour later two plod arrive in a car, and tell me to move. I politely explained to them that I believed I was legally parked. They admitted they had no idea what I was on about, but they would go away and check. They never came back, and I parked in the same place for the two weeks or so that the job took.
On a third occasion, I used an ordinary car for the job since there wasn't much room to park a van, yellow lines or not. As soon as I had parked, I spotted a traffic warden heading up the street towards me, as fast as his little legs would move, notebook in hand, and a look of disappointment came over his face, when I explained that I was an electrician working in a shop a few yards away. I was causing a bit of an obstruction, but by this time a delivery van had moved on from right opposite the shop, so with the warden's blessing, I moved on to the yellow lines there.