When you enter an Australian address it will only then remove the VAT from any items you have in your shopping cart that has VAT in the pricing
Below is an extract from the Amazon.co.uk page on VAT Charges
For dispatch to countries outside of the EU, VAT will not be charged. These packages may however be assessed for import or customs fees, depending on the laws of the particular countries.
Customs or import duties are levied once the package reaches the destination country. For certain destination countries, Amazon.co.uk will estimate and collect an import-fees deposit during the checkout process. These funds will be used to pay the import fees on your behalf to the appropriate authorities, when your package reaches the destination country. The estimated import-fees deposit will be displayed in the order summary in the checkout.
If an estimated import-fees deposit is not displayed in the checkout order summary, additional charges for customs clearance will have to be borne by the recipient. We have no control over these charges and cannot predict what they might be. Since customs policies vary widely from country to country, you may want to contact your local customs office for further information. See Customs Information.