Heating Gouldian Nesting Boxes

[Applefinch]

I breed Gouldians in Tasmania and the cold temperatures are not a problem for adult birds or chicks if hatched from November to say February. I did read that the parents can abandon chicks when it's cold, however they probably do so as the chicks have died.
If the parents keep the chicks warm all goes well, but I have had a few occasions where something causes the sitting bird to leave the box during a cold night and the chicks have died due to cold exposure.
Most of my birds breed during February/April with only a very few breeding in November.
I was disappointed a few days ago when I heard the birds flying about around 6am and at 8am I found the seven chicks in two boxes abandoned and dead.
I was wondering if anyone has successfully used heating pads under nest boxes or IR lamps and how it was done.

[finchbreeder]

Very well insulated boxes, e.g. a foam and wood sandwich type, would help.
Would globes just under the boxs on a timer work?