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I 've never been to Wales, but I'd suggest you consider living in the Midlands instead. Lots of cities and towns are literally next to each other, and it should be a lot easier to find a job. Rent and cost of living will be similar to Cardiff (i.e. a lot lower than London). Moreover, unlike Cardiff, there are a lot of flights to everywhere in Europe for when you fancy a bit of travelling, and even London isn't that far away.
If you're thinking of returning to Australia for a holiday etc within a year, you may want to look into a Round-The-World ticket instead. You may be able to go business class for not a lot on top of your economy price...