Let's get back to basics and ignore the negative nitty gritty. Is there demand for a direct PER-LHR service ?
Undeniably yes for QF patrons in WA and SA who want to avoid the gulf states and/or backtracking to MEL or SYD or taking codeshare flights on EK. Even if it involves a short across airport bus trip ala SYD. IT WILL HAPPEN but maybe not overnight.
I would expect load factors to be surprisingly good. Forget the crap about Paris etc.