Thanks to guides on the Internet, I was able to figure out the codes required to control the Kambrook RF3399 remote power outlet.
In Australia, this product is available from Bunnings: http://www.bunnings.com.au/products_product_kambrook-4-piece-indoor-powerpoint-kit-with-remote-control_P7030054.aspx http://www.bunnings.com.au/products_product_kambrook-single-indoor-power-point-controller_P4420192.aspx
I initially tried NewRemoteSwitch, RemoteSwitch, and RCswitch. None of these were able to detect this unit. So I used the manual analysis method by sniffing the signals.
I am happy to send these codes to anyone who wants them. I wasn't sure whether I should post it publicly in case it encourages the manufacturer to change the codes. I am very new to Arduino, and my coding skills aren't great, but it does work.
Something nice I discovered is that I can add extra codes that the Kambrook transmitter doesn't do (but still works with the outlets).. which can be handy in that it would make it difficult for a nearby neighbour to inadvertently control my outlets if he/she were to buy the same kit.
UPDATE 2: mike_linus has posted much better code for the kambrook control and sniffer. I haven't yet tried it myself, but I'm sure it's all good. Find it here: http://forum.arduino.cc/index.php?topic=178765.msg1720615#msg1720615
UPDATE: Maurie has told me that his transmitter's codes are different from mine. So based on this, I suspect all transmitters have different codes. The first 4 sets of transitions are the same with our transmitters, but the next 4 sets aren't the same. (Every 4 transitions I have grouped into a "set" .. e.g. "1101 1111 0011" is 12 transitions group into 3 sets). This is mainly a good thing, as it means you don't inadvertently control your neighbour's devices & vice versa. Arduino-wise what this means though is that if you are looking to duplicate your Kambrook transmitter's signal, you would need to sniff it first to find out what the code is. However, if you don't care what the Kambrook transmitter's code is, then you can simply use the codes in my arduino sketch and get your Kambrook GPO receivers to learn these signals. It just means you've rendered your Kambrook transmitter useless, which many wouldn't be too fussed about.