If you're in Perth, Western Australia, I'd suggest a visit to the Army Museum of Western Australia and the Western Australia Maritime Museum, particularly the Oberon Class submarine HMAS Ovens tour at the Maritime Museum. The RAAF Museum at RAAF Base Point Cook is also a good idea if you're in Melbourne, lots of vintage aircraft in the hangers there. And Fighter World at RAAF Williamtown in Newcastle.
I'll just add that there's no Imperial War Museum in Australia, the Australian War Memorial in Canberra is where you'd want to go
I'll just add that there's no Imperial War Museum in Australia, the Australian War Memorial in Canberra is where you'd want to go