An International Driving Permit is required in some countries, but NOT normally in Australia, for holders of a UK driving licence.
The individual country requirements for an IDP can be seen at the Automobile Association website.
Australia is stated as “IDP recommended”.
However, in my experience, not a single time have I been asked for an official translation of my UK licence (an IDP) by the Australian police.
A few examples of quotes on the subject:
This one being the most important and relevant, being from an Australian Driving Licence Department:
New South Wales
When driving in NSW you must carry your overseas driver licence. Your licence must be written in English or, if the licence is not in English, you must either carry an English translation or an International Driving Permit.
http://www.rta.nsw.gov.au/licensing/visitorstonsw/overseaslicence.html
Western Australia
If your overseas licence is not in English, it is advisable to carry an International Driving Permit or an approved English translation of your licence (if you have either of these) with you when you drive.
http://www.dpi.wa.gov.au/licensing/yourlicence/1365.asp
Australian Capital Territory
When driving in the ACT a visiting driver must carry:
* Your foreign driver licence written in English; or
* Your international driving permit accompanied by your foreign driver licence.
http://www.rego.act.gov.au/licensing/licenceoverseas.htm
Tasmania
If your overseas licence is not in English, you must also carry either:
* An International Driving Permit, or
* An English translation of your licence by a person accredited to translate.
www.transport.tas.gov.au
The same rules appear to apply in all Australian States.
Some other quotes
An IDP is essential when your normal licence is in a different language to the country you are visiting, and must accompany your VALID National licence.
An IDP is NOT a licence in itself, but effectively just a translation of your licence.
An international driver’s permit or international driving permit may be obtained from your home country.
This permit only verifies that you hold a valid license in your country.
It is your native driver’s license that allows you to drive in your or foreign country.
The translation of your license as well as an international driving permit or international driving licence also can’t be used in place of suspended or revoked license.
Persons going to a country to take up residence or employment, or for any reason other than tourism, should make enquiries about their personal position before relying on a permit.
An International drivers license (IDL) is proof that you hold a valid driver’s license in your own country. And it provides a translation into almost a dozen languages, mainly so that police and other authorities in other countries can read your license in their own language.