If you wish to travel to Australia for more than 90 days, and less than 6 months, for the purpose of tourism, then you will require an Australian Six Month Tourist Visa. Once your visa is issued to your passport, you have up to 12 months to enter Australia.

This visa allows you to enter Australia for up to 6 months from the day you first enter, and also allows multiple entry so you may leave and re-enter Australia as often as you like within a 12 month period from when you first enter (only for up to 6 months per time).
This visa does not permit employment during your stay in Australia, so you may be required to show that you have sufficient funds to accommodate your time in Australia (around £2000 - £3000).
You will not be allowed to study on your Australian 6 Month Tourist Visa for a period longer than three months. If you intend to study for longer than four weeks you may also be required to undergo a chest x-ray examination.
The cost of your Australian Six Month Tourist Visa is
£90.