The Adelaide Metro area is now a huge sprawl with many new suburbs popping up.
Work will probably dictate where you will live to a certain degree.
I live in the south in Onkaparinga Hills which is around 35 - 40 mins into the CBD depending on traffic.
I don't know much about the north so can't comment much but there are some lovely places there and we have a few friends up Athelstone and Salisbury Heights way.
So I'm not starting a North/South debate!
Down south here there are plenty of areas that are still affordable but around 30 - 50 mins from the city.
To name but a few (and look at surrounding suburbs).......... Hallett Cove,Happy Valley,Woodcroft,Port Noarlunga South,Seaford and Aldinga.
These are all popular areas with UK migrants.
Research is the key and then try and narrow down to North / South and then to just a few suburbs.
Once here you have to do a lot of driving around to make the final decision on what's right for you.
I think Adelaide has a bit of something for nearly everyone - just takes some finding at times.

