Campervan recommendations

Hi all,
2 friends and I are planning to travel down the east coast from cairns to Sydney, through December 2012.
There seem to be quite a few different campervan rental companies around so please can anybody advise on any in particular?
We obviously want to do things as economically as possible, so advice on which types of vans are more fuel efficient and also better in terms of insurance ( 2 x under-25yo drivers and 1x over-25) .
Finally, anybody that has done this - were you able to always sleep in the van or did you have to shell out for hostels sometimes.

Between 3 people - should a campervan work out more economical or would the greyhound be better?

Thanks!

Hey
I did 2 van trips while I was in Oz- first was Sydney to Brisbane and back and the Second was Sydney to Adelaide where we left the van. Both times we used Wicked Travel as it was the cheapest, but also the coolest vans (maybe your taste is different to mine but I found a beat up, crazy painted van was much more fun than a flash new automatic thing with a TV inbuilt), we paid around $35 a day for a 3 person van, which is pretty damn cheap. Also if there is a problem with the van they are brilliant and will drive you out a new one where ever you are (we did encounter one problem and we got a new van within a few hours). We did all sleep in it and we had enough room and it was comfy enough :) They provide all the blankets and pillows and at the pick-up site there are tables of stuff that other people have left that you might need- always plenty of pot noodles and washing up clothes! As for ecofriendliness, they prob arent the best as they are beat up old vans but as they are so cheap to rent, the extra petrol wont ruin your budget.

I mean taking the Greyhound might be cheaper but it certainly wont be as much fun, we met some amazing people when we were parked up in our little van, had an absolutely amazing time. But if you just wanna get to Sydney then take the bus but if you wanna enjoy the trip and explore the coast then take a van, you wont regret it :D

Hope this helped, Gracie xx