Does Oz have large Hypermarkets offering absolutely everything under one roof, sort of like K-Mart/Wall Mart?

Thanks.

Plenty. Big W, Kmart (no idea why they flourish in Oz), Target etc. However, I haven't found a Costco, although there are lots of local warehouse-type wholesalers that offer rock-bottom prices for just about anything.

Thanks for that. Kmart, Target, Big W is probably enough to keep the missus busy. i wont worry about Costco just yet!