Des,
Have found a beachfront ad in WA trading post ("The Quokka") for 100 per night at Palm Beach Rockingham (30min south of Perth, 2 to 5 min from Safety Bay) which may be the go for ya?! It is a little removed from the metro madding crowds and a really nice sail - bring weed fin due sea-grass!!
You can call them on 0412 608 784 or 08 9592 7560, another (non-beachfront) $100pn 08 9529 3600 0408 545 559. Reading on... Shoalwater "cottage" (= closer still!) $50pn (Crikey!!!) 08 9330 1917, mob 0410 416 213.
If you need, I could probably scan & e-mail maps if you get a street address...

http://www.windsurfingperth.com.au/travel/loc.html has a bit on Safety Bay under Perth section on "Lower West" part of map.
(Are we there yet??!!!!) Seaton