Wow, New Zealand. Been to Australia, stayed over a month while travelling around in a tiny rented RV, great place. They drove on the wrong side of the road there, I got plenty "thumbs up", so a guess my driving was pretty good? Eh?
Do the compression test with all plugs out and just wedge open throttle valve part way to ensure good intake air. To avoid any feed into electrical system trigger a direct power to STARTER side of the solenoid when you need to crank. That way all power will be isolated to only spin the starter. It cannot get back across the solenoid into the "HOT SIDE". Configure a jumper in a way so as not to arc at the starter, or at the battery, but touching 2 cables together in your hands in order to crank. You will, therefore, get no ignition or fuel anywhere and you won't have to disconnect any wires. Of course, the key will be left in the off position.