Speaking personally, if we were in Queensland at that time of year, we wouldn't be booking ahead and I'd be very surprised if you need bookings for caravan parks. If the council park (which is reasonably small) is full, across the road is the Big4 Hideaway caravan park.
Some motorhomes carry 'reserved' signs and leave them on site when they go out. Other people put their chairs on the site. Some caravan parks allocate sites and won't put other campers onto your sites.
Badger's site is www.home.vicnet.net.au/~badger04 - it's a great site for helpful information. If you still have trouble, try www.caravanersforum.com and use the link provided.

Kimby, the links I got were from "The Grey Nomads' Handbook", not the website.

I remember my Mum and Dad, many years ago, saying that the Council camping ground in Mission Beach was one of the best - in the days before they cost a fortune. It was the view, I think. (I finke?)

As for the Finke River, about 20 years ago, not having a 4 wheel drive, we got an exciting "Unimog" tour, from Alice Springs to Palm Valley, via Hermannsburg (an aboriginal settlement with a wonderful history), and I remember part of the actual road WAS the dry Finke River! If you are interested, look up Pastor Strehlow, a German missionary who controversially collected lots of artifacts, but also wrote down languages.

http://caravanersforum.com/badger.php
is the link that seems to work, from the caravanersforum site thanks.

Well, we're back, and we camped 14 nights (9 in QLD and 4 in a 2nd campervan in the Red Centre) and only stayed in a council caravan park one night (Palm Cove) in a National Park one night (Davies Creek on the Tablelands) and in Territorial Parks 2 nights (Ellery Creek Big Hole in the West Macdonnells and Henbury Meteor Crater Park south of Alice Springs). Every other night we "free camped", often all by ourselves in the middle of nowhere, at least it felt like it. We were never harassed or made to move on, and we never missed having power or other facilities of a caravan camp. Though we saw many campers at roadside rest areas, we never had to resort to camping at one of them.

Though we really enjoyed Palm Cove for our first night's stop with the campervan, when we got to Ellis Beach the next day we wish we'd stayed there. The campsites were right on the beach and there were no glitzy tourist hotels and boutiques like at Palm Cove. The next night we drove up the Daintree River road past the village and found a wide pullout next to the road to camp overlooking the river. Our two nights at Cape Tribulation we drove to the end of the pavement and beyond, camping at the ford where the 4x4 drive road begins.

When we headed for the Tablelands, we camped at the self-registering campground at Davies Creek (actually, since that is walk-in tent camping, we just drove back to the day use site and camped there, when it was clear that the day was over and no one was using it). After platypus-watching at Yungaburra, we camped by the river at Winfield Park near Malanda: there's a gap in the fence with a sign indicating "camping", so we weren't outlaws that night.

When the QLD Hwy Dept Map turned out to be wrong about there being a rest area that allows overnight camping at Etty Bay (and wrong about Mission Beach as well), we didn't want to stay in the caravan camp there so drove back up the road a mile or so and found a two-track road leading to a locked gate and parked there, taking care not to block the gate (and making sure it wasn't someone's driveway). Next morning we drove back to the beach and saw a papa and juvenile cassowary taking a walk. The Mission Beach council campervan was so crowded (though not full) and the smaller Bingal Bay one was totally booked, but we found a small boat launch site on Muff Creek that did not have "no camping" signs and settled in for the night. We camped at the very nice Babinda Boulders campgrounds, which did fill up that night. In fact someone in a smaller campground than ours snuck right in beside us to share our site without even asking!

In the Red Centre, our first night we went the "wrong direction" from Alice - I wanted to see a bit of the West Macdonnells, so we drove to the first place that allowed camping, Ellery Creek Big Hole, a lovely place. It did add an hour to the next day's drive to Uluru, though. We drove through the Yulara Campground and there's nothing wrong with it, except we just don't like campgrounds. Since you can't free camp at Yulara or at the National Park, we back-tracked till we passed the no camping sign as you approach Yulara, then drove another mile or so and found a two-track road that left the highway, and parked a ways off the road for the night. At King's Canyon we passed up King's Creek Station and the King's Canyon Resort campgrounds and drove out the Mereenie Road until the pavement ended and then some, finding a place to camp off the road a ways. Next morning we saw wild dingos and feral camels on our way back to the park for the Rim Hike. Then we drove most of the way back to Alice, spending our last night in the campervan at Henbury Meteor Crater park, with 3 other parties. (That road and the road into Davies Creek in QLD were teeth-rattling with washboards.)

All in all, we were pretty happy with our free camping/bush camping experiences in Australia. Though we felt we had to be a bit cagier than in New Zealand, and we didn't get to back up the camper to any beaches like we did in NZ, it was a good experience.

Thanks to all those who gave us advice!

Glad to hear you had a good holiday.

I'm glad you enjoyed it too, Kimby, and got back safely. Thank you for the report.