Choosing a housewarming gift can be difficult, especially if you don't know the couple's taste. Nature's Cutting Boards manufacture great cheese platters, cutting boards, bbq servers and other practical items. Check out their lovely products at www.naturescuttingboards.com.au. You can even order them online.
A plant is always a really nice idea. Get one in a gorgeous pot. Even apartments can fit a small plant inside or on a balcony. It brightens up the new place instantly. Put a lovely bow around the pot, they will love it.
I'd like to buy someone a Glasshouse candle or diffuser (can be purchased from David Jones). These are luxurious and come in a variety of scents to cater to everyone. My fave is the "Tahaa" candle which is the caramel flavour that usually permeates Peter Alexander sleepwear shops.
Or I'd like to buy luxurious soaps/gels for their bathroom which they could put out on special occasions or use for their own enjoyment! MOR is a lovely brand, Melbourne based and also caters to everyone, with some really exotic scents like "Italian blood orange".