Er, actually don't go to that list - it's not very discerning and includes bookshops overseas rather than better options in Oz.
Karen, I've not had much trouble finding books so would be happy to help you. What are your particular interests? Do you only want new books or are you interested in used books too? (This is the only way to get some of the more interesting works that are out of print.) Do you have a good independent bookseller nearby, the sort that places specialist orders?
I try to avoid using Amazon (US or UK), WH Smith etc in favour of local bookshops ordering stuff in for me. While you might pay full price for the book, the difference is made up in not having to pay international postage and handling. All you need to do is research the titles you're interested in, including publisher, publication date/year and, most importantly, the ISBN. Also research the price, so that you can be sure about the best option for buying the book (ie does the discounted Amazon price compensate for international postage and handling or is it still cheaper to place a special order?) Most bookshops I've dealt with prefer the UK publishing details to US but will look a bit further afield if pushed.
If buying the book overseas is the best option, check whether the postage is charged at a flat rate irrespective of the book purchased, or if it goes by weight. Also keep an eye on the shipment handling fees: some specialists charge so much handling it's almost cheaper to fly over and pick the book up in person.
Also, keep your eye on WH Smith who often have 'extra 10% off' sales including rarer UK titles, as this almost compensates for paying a book's air fare.
Some of the used book networks, such as www.abebooks.com and www.biblioz.com (Biblioquest.com.au), can be searched by country. Another way to cut down on postage - and support local businesses. BTW, you've got one of our most interesting maritime book specialists in your state: www.maritimebooks.com.au run by Jean-Louis and Janet Boglio.
For some ideas to get you started, check out the page of recommended sites on Mike Tennaro's www.titanicbooksite.com. There are links to bookshops, used book networks and bargain book sites. Unfortunately, not all of the bargain sites ship to Australia.
You could also check out the bookfinding section of my website which is written specifically for the Australian experience: www.bytenet.net/titanicimprint. While several of the shops I've plugged are Victorian, Hyland's also list their inventory on ABEBooks and the postage is only at Oz Post rates.