"willshak" wrote in message
...

I don't know about Australia, but here in the US we have "Great Stuff"
made by the Dow Chemical company.
I goes in as a foam, expands, and then hardens to a creamy color. It can
be carved after hardening.
If you have it there, be sure to use disposable plastic gloves when
applying it as it gets pretty sticky and hard to get off your hands.

And practice a little to get a feel for how much the foam expands, it has a
way of squishing out all over the place when it is over-applied.