Europe to Australia in 5 hours? ROFL. Who wants to go to Australia any way? [Maybe some would like to come back ...] Seriously, there are what ... 20 million people in Oz? Not exactly a mass market.
As for Mach 5 and the rest - has no one learned anything from Concorde? Supersonic flight over land is a big no no.
Haven't you heard? You don't have to go to Australia !
The Australians will come to the UK, and park their scramjets at Heathrow !
Last week at the 2011 Spaceplanes Conference in San Fransicso, they presented 3 papers on the next phase
of their 20 year development roadmap using scramjets and rockets for access to space entitled SCRAMSPACE
"(Scramjet-based Access-to-Space Systems) an Australian Space Research Program funded
project that represents the first phase of this road map. SCRAMSPACE is centred around an affordable, expertise
building flight at the scramjet entry point to the access-to-space Mach range (M8-M12). The flight will address
scramjet performance, materials, and instrumentation, supported by ground-based performance and vehicle control
developments in this range. Future phases of the road map will progressively incorporate scramjet technologies,
currently being developed in Australian hypersonics laboratories, into flight experiments of increasing speed and
sophistication. Ultimately, scramjet and rocket technologies will be brought together to demonstrate a prototype
hybrid rocket / scramjet access-to-space system".