It wouldn’t be too difficult to extend the Singapore flight onwards, currently it operates four times a week. However there’s lots of competition between the UK and Australia and at least one airline is having a sale when you are booking. When it’s low season in a particular country and origin/destination traffic reduces, the airline simply goes into “hub” mode and sells cheap connecting flights instead. During high season they will sell a return ticket to someone visiting their country from the UK and another return ticket to someone visiting their country from Australia, other times they can sell a return from the UK to Australia via their country.
Peak periods differ so there is almost always an airline discounting to fill seats.
On the UK - Singapore leg, only BA and SIA are nonstop giving Norwegian and advantage against other airlines. However between the UK and Australia, everyone has to stop once which puts them head to head with most of the Asian and Middle Eastern Airlines. Once you add in luggage and food it might be better to look at China Southern or Malaysia Airlines.
Last edited by krismiler; 16th Feb 2018 at 01:18.