I've posted this on living overseas and gotten some good tips, but thought perhaps there might be more direct experience here.
Looks very like we will be moving to Perth early next year and we'd like to get a nanny. We have the MOST AMAZING nanny here but sadly she can't move with us, her husband is not keen and it might be very difficult with visas anyway.
I wouldn't be at all worried if we were moving to Sydney or Melbourne but it seems from speaking to friends that nannies in Perth are very unusual. GUm tree seems to have mainly ads from au pairs/mother's helps who work part time or school pickups, and we'd need full time care.
We are obviously never going to be able to replace our amazing nanny (sniff, sniff) but we would like to get someone like her - ie, experienced, English-speaking, someone who sees it as a career and not a job to do while you are at uni. Daycare and au pairs won't work for us at this stage for a variety of reasons but au pairs might be good later on.