Tutmae - I'm in Perth too and had May babies. Both my girls were in grobags from about 8 weeks and 4 weeks respectively. Depending on the weather, in winter they would wear either a singlet or short sleeved bodysuit under one of those bonds all in one suits, then the 2.5 tog grobag. Then they would have a sheet and either a cotton thermal or fleece blanket over the top.

PP is correct in that they recommend not to use blankets but I always have without any problems - you just need to make sure you keep an eye on how warm your baby is getting - and with a newborn you will be up a lot for feeds anyway so its pretty easy to keep an eye on them.