If you're delivering at the Matilda, you may want to hold off on buying diapers as they will provide you with three big packs of it while you are there and any unused ones can be packed up and taken home.
(From other posts it seems they are now using Pampers - although when I was there in March, we were given Huggies.)
The other advantage to waiting is that you can then see what size your baby is before deciding. If your baby is on the smallish side, then Huggies tend to fit better while bigger babies do better with Pampers.