Hey Joris,
Plenty of excellent spots to sail, and boards are readily available - just be aware that the exchange rate makes everything a little expensive at the moment if you're traveling on the Euro. Cars and vans are not cheap here anyway.
As well as the minivan idea, consider a Holden Commodore Wagon...
www.gumtree.com.au/s-automotive/perth/commodore+wagon/k0c9299l3008303Massive enough to sleep in with your kit, a bit safer (in my opinion) and every aussie mechanic can work on one in his (or her) sleep.
If you're going to be based in Geraldton then you may want a freestyle board as well as there are some great options around for when the swell isn't in.
Enjoy!