That looks like an older Range Rover to me. Not sure if this will work in your Australian model, but what I use rather than buy a special tool is to pilfer a set of hanging file folders from your work. The metal pieces that hang the folders are the perfect thickness and they have a notch cut in the end that engages in the locking mechanism perfectly. Just get a pair of these metal rods and insert one in each slot with the notch towards the bottom of the radio. They should slide right in and latch into the locks. This will release the tabs on the radio and you can pull the radio right out. I just slide a couple of fingers in the cassette opening and pull up. Just remember to remove the metal tabs before you reinsert the radio.
I guess you would have the same type of office supplies in Australia.