Assuming you have a variac, if you have an ampmeter or wattmeter you can determine what the transformers are designed for without any load on them and without risk of damage.
Remove all the tubes, and then power the set from the variac through the meter. For convenience instead of using my DMM I use one of these:
http://www.p3international.com/produ.../p4400-ce.html
They are sold for people to monitor power usage around their house. I assume you can get a similar device down under.
Slowly ramp the voltage to 110VAC. The transformer should only be using a few watts in parasitic losses. Now very slowly start ramping up to 220VAC. If this is a 220V transformer the parasitic losses will stay at only a few watts. If it is a 110V transformer, at a certain voltage, probably around 130-140V, the transformer core will saturate and the wattage will climb dramatically. If you hit around 50W don't go anymore to avoid damage to the transformer.
This procedure will tell you which transformer you have.
Darryl