Sam
I'm going on this trip on 11th October. Our guide Sarah Wrightson offered this advice:-
"Can I recommend that you don't take too much with you.
Don't attempt to take enough clothes for the 3 or 4 weeks - just take enough for 7/8 days because every hotel has laundry facilities (self-service washing and tumble drying machines) and you will have time to put the washing on and leave it to dry overnight if you don't want to use the dryers. Plus every room has an iron and ironing board, as well as a kettle. So you can leave these items at home.
Go with a lightly filled case as you'll find lots of souvenirs and gifts to pick up throughout the tour.
Sarah "
Half way through the trip we spend four days in Cairns. I'm planning on getting my laundry done then, so I only have to take 10 day's worth of clothes with me. I'm not one for souvenirs but I usually find what takes up most space is my toiletry bag!
Hope this helps.
Sally