Ineos Australia responded to my trailer socket/plug question which was most welcome. (Thanks Justin)
For Australia the brake controller wire (service brake) will be allocated to pin 12 on the Euro socket.
If you wish to retain the old Aussie 7 flat plug on your trailer (which really defeats the purpose of having the best trailer socket on the car and worst plug on the trailer IMHO

) then a quality 13 to 7 adaptor will work. This would mean buying an adaptor that has the diodes built in and I believe the Narva one has this - some of the cheap ones might or might not have diodes.. who knows...
If your trailer/caravan has left and right side light and tail lights joined together which is typical in Australia and you wish to change your trailer/caravan plug to the
far superior 13 Euro plug, then you will need to buy the 13 Euro plug and put diodes in the wires of the side/tail lights that are joined so there is no voltage feedback to the vehicle.
Ineos recommend leaving the vehicle as standard which means placing the diodes in the wiring of the trailer/caravan. Easy as. Here's an example I found of two diodes in a 7 flat socket - just an example as mine will be the 13 Euro round trailer plug. Hope this helps the trailer wire situ in Aus at least.
On an aside... your brake controller will likely need a diode also and if you are using Redarc it is placed in the red wire. (redarc sell their diode with instructions)
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