Let's have a little discussion involving the butterfly effect.
In 1770, James Cook discovers the east coast of Australia, which he names New South Wales and claimed for Great Britain, declaring it 'Terra nullius'. The British know Australia exists, but they decide to leave the continent alone.
That changes in 1783, with the British losing the American Revolutionary War, and as a result, their American colonies. With nowhere to send their convicts, the British government dispatches Arthur Phillip and the First Fleet to set up a penal colony in New South Wales.
So, the British defeat in the Americas is what prompted them to establish a presence in Australia.
So, let's answer this question: If the American Revolutionary War either never happened or the British won the American Revolutionary War, do the British still colonize Australia (to a much lesser extent) or do they leave it alone?