I have booked tickets ex EU a number of times, but do not book journeys which involve backtracking. Going to Sydney starting in , say Amsterdam, with a separate ticket to Amsterdam is only about an extra 25 miles on a journey of 10900, but makes a great cost saving, plus allows starting from Gatwick or City rather than Heathrow. Going from City offsets the time connecting given how quickly I can get to City when starting journeys in UK

I have in the past for a v large saving done backtracking, but there would have to be an extremely big incentive to do so