Non-stop flight from UK to Australia will happen within two years, says Qantas | Home News | News | The Independent
The ideal timing would be an early evening departure from Perth, arriving around noon next day in London - allowing plenty of time for connections at either end. The return flight would take off from Heathrow around 3pm, arriving late afternoon the next day in Perth.
They propose this on the 787-9, but I'd ask about their window control protocol first ...