hi northy..
As a beginer in the waves go to Geraldton, coronation beach ).. it is perfect for you.. i had my first proper wave seshs here and I was in paradise..... sept maybe a bit earlier for scoring decent winds though... better oct to nov. Take everything you can gear wise just in case it's light on the wind. Take your camping stuff with you and you can pitch up where you windsurf...perfect
I'm going again in oct, might see u up there

never sailed gnarloo, so someone else maybe able to give advice on this... but from what i've heard and seen it's more for the advanced... it's one of the best windsurf waves in the world ... but if you get caught in the impact zone .. you and your gear will get a decent workout and at time of the year it will be huge and powerfull nearly every day..... see what i mean
www.seabreeze.com.au/gallery/gallery.asp?imageid=804