On our Perth and WA trip the only pre-booked accommodation we made was for our first 2 nights, at the Rydges Hotel. We chose the majority of the many other places we stayed from info in our Lonely Planet Guide, or from info at the various Tourist Info Centres. There'll be info on where we stayed in my travel log, which will be added soon.
A good central location within walking distance of the shopping malls and the Swan River. Theme: HotelComparison: more expensive than averageOther Contact: www.rydges,com.au