Upvote:4
Personally, I would try to ignore the normal postal officse. They are often quite expensive when it comes to posting a parcel. Often you don't have choice and then it actually doesn't matter in which country you post your parcel. Most public postal organization more or less use the same logistical infrastructure.
Another option would be the big guys, like DHL, FEDEX, etc. Still it costs.
Another alternative is go to a city where there is a large immigrant population originally from the country where you want to send your package to. Usually concentrated immigration groups cause a healthy parcel stream to the country of origin. This allows for quite lower postage rates then when sending it "traditionally", since different small businesses just rent container space in either a freighter or an airplane and are able to fill that space regularly. This company (you need google translate) will for example send a box of 160l in volume to Indonesia for only 60 euro. With sending by sea, it is all about volume and no weight. With airmail you pay per kg, but still the rates are rather low compared the the postage fees. The company mentioned earlier mainly caters an immigrant population originally from Suriname. They are able to send a package to Surinam for 4 euro per kg by airmail.
I would expect the largest Australian population in Europe would be in London, so my best bet would be that sending through the UK would be your best option for sending from an european country. In an slightly related question a london company is mentioned, that could be an interesting option for you as well.