Hi Canter!
Did you visit this webpage on the net? I recomend you to take a look:
http://www.tourspain.es/ About taking trains...and being Cantabrian (Spaniard from the cantabrian region, Northen Spain) I must tell you that you must vist the north and the best way to see at least something is taking the Trasncantabrico.
http://www.transcantabrico.feve.es/ It is a good way to have an incredible trip in the Green spain (Northen Spain) and have a 1st contact that will make you come back again.
You can visit other parts of Spain...and I am sure you will be nicely shocked about the gourgeous differences that you can find in such small country compared with Australia.
Let us know what did you decide to do finally... Hope you will have a pleasant time over here.
Iker