There seems to be lots to be saved in doing things yourself, such as most of the buid, however there are some things it is worth paying for, especially if produced efficently in large volumes, even if not on site. This could be potentially said for making all of a timber frame house in a workshop, and bringing to site once ready.
The thing with making up muck, is that the size of the mixer will determine the time taken.
It is worth considering the relevance of using so much concrete, and what other options are available. Cement used in concrete is a vast consumer of energy in its making, and it may be worth discussing what you plan to do and see if anyone has any advice on alternatives.
