By Overland Tour
There are a couple of expedition companies such as Ozbus or Exploratory Overland Expeditions that conduct organized trips from London to Sydney but the last leg of the journey involves flying to Darwin from East Timor or Singapore while the bus is shipped across. These are targeted at backpackers able to take months for the trip.
By plane
Australia is a long way from anywhere else in the world, so for most visitors, the only practical way of getting into Australia is by air.
Approximately half of all international travellers arrive first in Australia in Sydney, the largest city, IATA: SYD; ICAO: YSSY. After Sydney, significant numbers of travellers also arrive in Australia in Melbourne, Brisbane and Perth. There are also direct international services into Adelaide, Cairns, Darwin, the Gold Coast and Christmas Island though these are largely restricted to flights from New Zealand, Oceania, or Southeast Asia.
To Sydney it is a 3 hour flight from New Zealand, a 7-11 hour flight from countries in Asia, a 14 hour flight from the west of the United States and Canada, a 14 hour flight from Johannesburg, a 13-16 hour flight from South America, and up to a 24+ hour flight from western Europe. On account of long journey times from some destinations, some travellers from Europe opt to have a stop-over, commonly in Singapore, Hong Kong, Dubai, Bangkok or Kuala Lumpur.
If you have to change to a domestic flight in a gateway city, Sydney, Brisbane and Perth all have distinct domestic terminals, requiring some time and complexity to transit, check the guides. Melbourne, Adelaide, Darwin, Cairns and the Gold Coast have all gates in the one terminal building or within easy walking distance of each other.
By ship
November to February is the cruising season, and there are usually about 10 ships that arrive in Australia from other countries during this time. You can cruise to Australia, and then fly home.
Holland America Line, Princess Cruises and Royal Caribbean, all offer cruises to Australia across the Pacific.
Alternatively, you may sail to Australia in your own yacht, but beware of customs regulations. See Australian Customs for details