I'm want to replace the light below with a smart light that only has two wire connections (live and neutral). The 3 core wire is connected to power, red is live. The 2 core wire is going to a switch (controls this light and another, separate one).
Not sure what I need to do with the white and black wires? Any help appreciated!
Two-wire and three-wire, (or core) cable, not phase. Pretty sure you're likely to be only single phase on a domestic lighting circuit, though you may have 3-phase to your house, depending on local practices.
I'm not adequately familiar with NZ practices to be certain, but the Green/Yellow is pretty nearly universally Earth/Ground, not neutral, and I believe that in the Commonwealth old style Black is neutral, so if Red is live, White must be switched live.
Thus, presumably your current fixture has Green/Yellow earth, Black neutral, a point where Red live is joined to Red live to the switch that is otherwise not connected to the rest of the fixture, and White switched live from the switch to turn it on.
The black and white wires are the ones that supply electric power to the lamp, so you need to connect them to the lamp.
The red wire branches off to the switch and comes back up the white wire to power the lamp.
You're going to need to link the two red wires together. I'll suggest lever connectors like "WAGO 221" or "Biz line" because they're hard to mess up.
Recent developments suggest that getting the correct torque is important on screw connectors so I'm not recommending them.
So far as I can tell wire-nuts are not approved for use here.
The ground wire should connect an earth terminal if present, the body of the fitting (if it's metal) or else be insulated (you could use another connector to insulate it)
If you need more room for all these connectors you could use a round junction box (they are about the same diameter as the lamp base pictured.) or try to match the size of the net lamp's base.
