Hi,

I would be unfamilier with an Australian model.

we opened up the freezer floor and what do you know.. the coils
are all iced up! so with my hair dryer we melted it. Now we cant hear
the defrost heater working at all

If the defrost timer was not moving or bad, if the defrost heater was
bad, if the defrost thermostat was bad ( or any combination of these )
the refrigerator will stop defrosting and the cooling coils will plug
up with frost and you loose your cooling ability.

Could this have been the problem? defrost heater doesnt work means the
timer doesnt work because they are connected - or are these 2 seperate
problems?

Could very well be relaited!

Someone more familier with the unit may be better off to help....
http://www.applianceaid.com/UK_appliance_links.html

jeff.
Appliance Repair Aid
http://www.applianceaid.com/