On the subject of Australian policy, this fromt the Sunday Times presents a more nuanced picture -
"The policy was drawn up with help from an Australian strategist, Isaac Levido, whose mentor Lynton Crosby masterminded many an election victory there through using a “stop the boats” message. The apparent success of the decision by Australian MPs in August 2012 to process all refugees offshore in Papua New Guinea and Nauru — a tiny island state in the Pacific — is often used as proof that Rwanda can work.
Yet the data paints a more complex picture. In 2013, the year after offshore processing was introduced, the number of small boat arrivals grew, from 17,204 to 20,587 – a record high.
It was only when the Australian government, by then led by the Liberal prime minister Tony Abbott, launched Operation Sovereign Borders in September 2013 that numbers started to fall. Under this new policy, boats were intercepted and guided back to safe countries. By 2014, only 450 people arrived by sea; the next year, the policy was so effective that no more boats were taken for offshore processing."
So offshore processing wasn't the easy answer.
It also cost 100s of millions of dollars and led to a series of highly expensive of law suits regarding poor treatment.
The UK Government will have conducted assessments of the likely success and overall cost of the Rwanda plan and yet none of these have ever been published.