Saad first came to assess the job, and estimated it would take about 4 hours as it wasn't a straight-forward installation. His quote was most competitive (i've had 3 others).
He came on the agreed day with the material, and explained what he was doing at each step of the process. He was polite and knowledgeable.
He completed the job, tested the heating system and only left after he made sure it's all working fine.
Job well done. I will definitely ask for his help again with any plumbing or heating works, but hopefully not anytime soon :)