Really it is a willpower thing. The UK is not prepared to show some willpower in preventing illegal immigration while Australia generally is.
To quote John Howard...
Australia has quite a large asylum intake and takes people from various places such as Burundi, South Sudan, Myanmar, Latin America, I have even met a Czech and a Bosnian refugee as well as the Middle East rather than these self funded 'boat people' arrivals.we will decide who comes to this country and the circumstances in which they come.
Not always been a success as the overseas processing in Nauru and Papua New Guinea has been considered a failure as the centres are being closed and people require complex medical treatment in Australia.
From what I understand, any illegal boat arrivals from Indonesia are transferred into a lifeboat, presumably more seaworthy than the boat they chartered to make the journey to Australia, then towed back to and cut adrift just outside Indonesian territorial waters, where tidal currents will carry them back to shore in Indonesia.