Are you going to be using a major registered builder like henley homes etc or is it a mates build type thing?
There are huge differences in how BICOE funding works depending on who's building it.
The long and the short of it, try to keep as much of your deposit free for the construction loan, not the land loan.
12 months apart they will be 2 separate deals.
So maybe use $30k max to pay deposit and legals for the block and keep as much of the remaining $70k as possible for the build.