Woody, I spoke to the builder this evening and he asked me on what basis am I judging the amount of works done. I told him it’s obvious just by looking at the place!
I wonder if you would be better off instructing a building surveyor.
The surveyor could not only do your foundation detail and help with the build over agreement, but he could advise on everything else about the work including permissions, drawings, processes, building control inspections, payments, costs, quality - everything really.
Your previous post mentioned that the builder recommended a specific building control officer, in which case that implies a private inspector, not the council's inspector. This, in turn, could imply that the builder and inspector are friends, in which case the inspections may be lenient in the builder's favour.
Again, a surveyor would be able to advise on this.
Cost wise, you need to come to some arrangement with the builder for him to pay for all your additional expenses which are directly related and caused by his work and his failures.