I communicated very very carefully that I needed boiler install, flushing, flue install and commissioning. I walked him round the house detailing pipe and rad routing/sizes etc, he was very happy and asked no questions other than where I wanted the filter.. Didn't quite get it properly behind the washer with best access but location was acceptable.. Just. I even marked up the wall with a rough plan... Never got followed. He put gas feed as lowest pipe meaning hot output had to crossover... I could go on and I'm sure if you had first hand view you'd agree it's a dogs breakfast but we're warm and it's recoverable but not without another spend..