Thanks @bank . Much appreciated. Agree with you on keeping the screw piles if there is a loose fill. Will ask the builder for more information.

Sorry for the long post. We recently bought a land in Berwick Waters estate and we are in the process of building a ~28 SQs single storey home with Carlisle homes(CH). Initially we were quoted 18K as site cost and now we reached the tender stage and the new site cost is 31K. The reason for this site...