Maybe change the thermostat and see if that fixes the problem like it did for BadCo.
Before chasing down a sender.
The temperature sender part number is AYG 9603 (Which seems like a Landrover number, not an Isuzu one)
which is odd as I can't find that number on any supplier sites (lrdirect.com etc)
Maybe you have to get it from Land Rover themselves.
Found this ancient thread from Bearman
http://www.aulro.com/afvb/isuzu-land...re-sensor.html
That number, PRC2506, does come up, but I really don't know that it's the right one for a Perentie.