The best time to go to Australia varies depending on your itinerary. Most of the country can be visited all year round, except for the tropical north. The tropical north has wet and dry seasons, so the best time of the year to go is from May to September, when the region is hot, dry and accessible.
The warmest temperatures are during the Australian summer, from around November to February, and this can be a great time to visit. Keep in mind that the red centre can be very hot during this time. For milder temperatures in the red centre, visit between March and May.
For all other regions the best time is from October to April, though visiting during the Australian winter (June to August) can also be a good idea, as temperatures do not plummet to the same levels as in the UK, and there are fewer tourists to compete with.