I live near Heathcote and I bet its cold at the moment. First thing I'd do is turn the heater right up on the CC then check that the heater valve opens and the pipes to the heater core get hot.
My heater used to only work on full 32 deg heating- that was a stuck motor/limit switch on the mixer door- the control is on the passenger side of the heater box.
Then later it stopped heating- that was the stuck heater valve.
With the CC computer it is better to start with the obvious and easily checked then work back. That computer needs a a few different inputs to be right before it opens the heater valve.