About sixteen years ago I had a problem with a National House builder who wouldn't take me seriously:
I had my solicitor take out a High Court claim against him which costs very little to issue, but a hell of a lot more to defend. I backed that up with a letter to the local paper (they did an article) and set up a meeting with the NHBRC (useless) The local Building and Planning regulators (excellent) my own surveyor and the people from the builders.
One problem is that so many people connected with the building trade: Estate Agents, builders, NHBRC, surveyors and even solicitors seem to believe that because it is a building, the normal laws of contract don't apply. You have to pay exactly the price they want on the dot and they think they can screw you around as much as they like.
Wrong!
I finished up being entirely satisfied with the house-but it takes effort.