Okay, so the build contract date becomes 22/05/2012. It's taken ages to get there, what's that, 13 weeks on, but finally it's sorted.
The next thing to do is make sure settlement for the land goes all smoothly, which is this time next week.
Hopefully after that I can put most of everything behind me and just let them get on with building me a house! Oh, and start paying loan payments ;p