How do I wire this Australian ceiling light?
Warning: Contains Dangerous Discussion.  Call an Electrician.

I did a quick search on Australian wiring, and found out that A is "Active", which would be considered HOT in other countries.  N is Neutral, and Loop is for carrying on to other outlets or switches.

This link https://www.dlsweb.rmit.edu.au/toolbox/electrotech/toolbox1204/resources/04diagrams/04lighting/05loops.htm shows loop being used, in two different instances, on both the neutral and the Active sides of the circuits.  So in your situation, the best answer can only be: It Depends.

My suspicion is that there is another light connected to this one -- Did two lights turn on at the switch under the old install?  If so, you need to pigtail (See below) the Loop wire to either the A or N wire (But we don't know which!!!) to carry on the circuit to the other light.  

My starting assumption would be that the Loop should be pigtailed to the A, but it's dangerous just to go ahead and try that.  You have a 50% chance of being right, and a 50% chance of shorting out the circuit.  Hopefully, this would result in a breaker tripping, but it could result in a fire.  So call an electrician.

Pigtails - Two wires in a circuit twisted together with a small (4-5 inch) length of wire. Typically this is used to both carry on the wiring to another device, with the small length being used as a tap, feeding the local device.  All three wires are twisted together with the appropriately sized wire nut.   http://electrical.about.com/od/wiringcircuitry/ht/pigtailwireconn.htm