So part of the story is a few years old, and the Labour councillors in question happened to get away with it at the time, so what? I'm with you. Clearly something needs to be done about this whole mess, the question is how best to approach it.
I suggest that the answer to the issue of land banking is to introduce a "land value tax" for builders. That would stop the developers from holding onto the land for any longer than they needed to. The tax could be payable only in the case of dwellings being constructed on the land while it was owned.
As for the question of poor quality building and conflict of interest in NHBC inspections, the answer is to set up an independent government funded inspection agency. Maybe we could use the money from the land value tax to do this?