Perhaps not far enough out? You are heading north with those two areas also. South and east opens up a whole load of other options. People will still travel to those places you mention with relative ease.
You say two hours so perhaps look at places like Mannum, Murray Bridge, Myponga, Tailem Bend, Port Wakefield, Wynarka? Those sorts of towns are all a good 60-120 minutes away from suburbs in their direction out of the city IYKWIM. I put in Port Wakefield to google maps and put West Lakes as the starting point for example. Mannum I went with Hallet Cove as a starting point. I've been to all of those towns at some point (apart from Wynarka) since moving here (some not for more than a couple of hours at most but that was enough to know they were not somewhere I would want to live in or spend a lot of time in but passing through was fine. Country towns here are so very different to the UK and I am not suited to them nor they me ).
I have no idea about the employment agencies. Most of what I know is because I know teachers who talk lots about how the system works (or doesn't work) and much of it seems to be word of mouth and having a foot in the door and getting your CV out to schools.
Most people don't want to work rural or country, hence them staying in and around Adelaide. The job market here seems to be saturated with teachers atm. So many young newly qualified ones and many who can't get work or can only get relief stuff.
Hello me again - the MiL is still looking to move over here permanently but we have an interesting question regarding Wills. If she has made a Will in the UK does that have any legal rights in Oz? Would she be better to make a Will in Oz?