This is a serious way to complain: hang a sign on a busy road with a list. I feel for the owner as there are more stories of quality problems with house and this is not a cowboy builder, if it's the one I think it is – Kier.
The last time I had a serious complaint with a builder was when we had a conservatory built on our Annex. I got so little response that I had to put together a website listing all the problems, complete with detailed photos, omitting only one thing – the name of the company. I threatened to insert the name and that got their attention.
The extra photo is a closer view of this list . . .