I am in Perth also and I use a sleepsuit but not a grobag brand. It is 1 tog I think, and I also have on DD: a singlet, long sleeve bodysuit, all in one pjs, a sheet, a wool blanket and two brushed cotton blankets. If I feed her during the night (usually do!) then I also turn on her oil column heater at about 3 or 4 am. Not really answering your qu but just giving you an idea of someone in the same location. You could try a blanket on top. Just check how he feels when waking up...