You seem to be only considering west bound flights ex Australia - there is the alternative of going eastbound.
Have a look at some of the round-the-world fares that are available (notably Oneworld QF/BA/AA given that you may want to do some flying around the UK which could be included in a r-t-w ticket) sometimes these fares compare favourably with point to point AUS-UK-AUS fares.
Also these tend to be far less restrictive should you need to change travel dates.