Hi, I have read alot of differant stories on this site and other sites about babies who move around in their cots alot. When I first put my boy in the cot he too moved up to the top so I started to use a t-sleep (www.safetsleep.com) It is a device which wraps around the cot and in the middle of it has a part which you wrap around the babies middle to stop them moving up and down the cot. This has saved my life and also I think he enjoys it now. It only took him a few days to get use to it (as he would try to escape from it) but would be a much usefull investment. I presume you can buy them over in Australia.
Deena NZ New mum