Australia flights - best way to do multiple stops

[habloingles]

We're planning an Australia trip for July/Aug 2020. We want a Singapore stopover, a few days in Sydney, then to head north for Brisbaine/Cairns (ideally both, but Cairns would be preference as we want to go diving) then home again to London.

Is it more cost-effective to do a multi-hop with a single airline or to just book flights to, say Sydney, and then get internal flights?

Any advantage in booking through an agent?

I book this an open jaw flight, with a separate booking for your Sydney - Cairns and/or Brisbane bit. I search using Google Flights, selecting a multi-stop trip for the three flights: home - singapore; Singapore- Sydney; cairns/ Brisbane - home. I then book it directly; no agent involved is A LOT cheaper.

We booked through BA last year and was a lot cheaper to book multi flight than individually.

If it's not all one booking be careful with luggage allowances. Domestic flights will give a lot less baggage allowance than long haul so you may end up paying extra (Jetstar is like Ryanair in that everything costs extra although they are fine to fly with). The other disadvantage of booking separate flights is if something goes wrong and you miss a connection it's on you, if it's all one booking the airline has to sort it out. Singapore Airlines are my favourite airline Europe/Aus and you can get some good deals on Singapore stopovers if you fly with them.

Get on skyscanner or similar, and try it out! You want multi city - either with or without the Brizbane/Cairns bit.

We booked:
Out - Home airport-Abu Dhabi-Melbourne.
Back - Sydney -Abu Dhabi-Home.

Cost the same as a Sydney return. Then we used JetStar and someone else to do 3 internal flights. Yes to watching the luggage allowances if you use the local airlines.
For us, using the local airlines saved a lot of money.