From Wanneroo you'll probably sail Pinaroo Pt initially... pretty close, about a 15-20min drive. Lucky too, as you will be on the road to Lancelin which is sh!thot and only about 40min from there. Poor southern suburbs people have a 1.5hr drive.
All the shops carry second hand but that will be a bit of a drive, 30min - 45min ish.
There will be tons on seabreeze about Oct all the gear starts moving. I have a few Simmer wavesails, an EVO80 and a OES 80 (waveboard) for sale

Wettie for summer, coming from the UK you probably won't use one. I use a 2mm springsuit in summer unless up north i ma wear boardies and a thermal rashie.
a 3 x 2 steamer for winter is plenty