if you want to see how to setup a central door locking mechanism go to the site listed below, and join the forum there. They have on-line schematics for adding in user-built central locking/unlocking mechanisms using a couple of relays. I know this isn't what you want to do, but their schematics might help you trace out the problem.
www.the12volt.com
On the US version the door lock module w/relays is behind the glove box, and requires the security module to be removed before you can get space to undo the bolt holding the door lock module. However, since this is a side-for-side swap between US & JDM I wouldn't assume the module placement is in the same place. Perhaps the other folks in AU or NZ can jump in on wiring/component locations.
Also, as an aid, I have included some info from DEI on their alarm systems and how they interface to door locks. The US SVX is definitely negative triggered.