Alternative prices ?

I was getting more and more frustrated with constant changes in the build price and confusion over markups of subcontract costs. So I decided to send all the drawings to an alternative builder. His initial reaction was there was potential for some cost savings - but so far I have not received the figures yet. Changing will not be easy especially as we have now just been given the go ahead and the last thing I want is more delays. I might just need to proceed with stage 1 while I pin down the prices for the rest and see if I can change at a later stage. Will post again once I have the alternative quote.