I bought one in Argos just before the recent catalogue change and find it good.
The most important thing to remember to check for before buying are the free lifetime map updates.
The one I bought seems to have gone out of the current catalogue but seems similar. In the reference code 2545 LMT the L stands for lifetime maps and the T I understand is for traffic warnings. All the ones with 5 in the reference code appear to stand for 5" screen which seems to be the widest with Garmin.
I think it is only working for Ireland/UK at the moment as I would need a memory card to upload the Western European maps which I am not interested in.
I love the constant speed limit shown on the screen and the updates about speed cameras in the area.
I had a quick look at the Halford site and some of their models seemed older than the Argos ones.
Power City and DID sell them also as do Amazon. I think either DID or Power City do TomTom only.
Make sure to check out the online reviews before you buy and the Argos site may have some for their models - both the Irish and UK site. [broken link removed] is handy for checking stock.
Not sure about your chances of getting Australian maps.
I've heard that there are ones that you can change the voice because I will admit that 'Madge's' voice as we call it would wreck your head. I would put her on a par with 'please remove your items from the bagging area'
The mistake that we made with our last Garmin was that it did not have the map updates free of charge and they would have worked out as expensive as buying a new one over time.