I can't answer your question completely, but I can provide some thoughts ...
Perth is a very geographically isolated capital city - but very closely connected to Asia. It takes about the same flying time to go to Singapore as it does to Sydney.
Depending on where you live, Perth has decent public transport into the CBD, but it is a very spread out place. Our main metro train line spans 110km end to end (Butler to Mandurah). It is cheaper to live in the outer suburbs; however, you need to add in your travel time to work.
Of the three other cities you mention, I have only visited Sydney. It is busy, and exceedingly expensive in terms of cost of living (worse than Perth). I hear only good things about life in Melbourne (besides the wet weather - but if you are coming from the UK, you'll be used to that). The advantage of living there is the easy connections to the big cities on the East coast of Australia.
As to work opportunities for a tech data analyst, I'll leave that to someone with some knowledge of your industry. With the decline of the mining boom in Western Australia, jobs in Perth might be a bit scarcer - not sure.
Good luck with the research.