Telkomvision should be no drama at all in Darwin.
You wouldn't need that big a dish either I reckon.
Here near Brisbane you can get it on a 3 meter dish so a 2.4 or even a 1.8 might do you up there.
Telkomvision is not a circular signal so no need for a circular LNB.
Circular LNB's are really no different anyway. All you do for circular signals is insert a dielectric plate in throat of your LNB. Quite often though if you have enough signal strength you can just receive a circular signal without that.
Please note though that Telkomvision is encrypted with 1rdeto2.