I shopped and shopped.
And shopped.
I think it may actually depend more on the sales person you get than the builder itself, but I finally found a builder who made a deal.
I ended up with about 30m2 more house and slightly more inclusions.
So all in all I am pretty happy with the process though it was time consuming.
I think a key I found in this process is to look at all blocks on market as resale or onsale, (looking for a discount to market price) but don't buy yet, find a house on sale in Home or similar magazine that fits the block, then do the deal on the land and seal up a deal on the house. Make sure you talk to a sales person first to make sure all inclusions you need are in. (Think lighting, carpet, tiles, paving, remote garage doors, etc as they are not always included in price)
If your going to build in Bunbury let me know and I'll pass on his details.