SW-WA

I am planning a trip to South West WA on March-May 2015. After countless calculations to go by air, renting a camper van or a car, stays and so on, I decided to go with my Patriot and Sportliner, 10-12 days to go smoothly and the same back, about a month staying there. I am planning to arrive to Kalgoorlie or Hyden, and then stop around Perth on the way to the Cervantes area, Later do all the coast down to Albany before returning home.
Unlike QLD where there are countless National Parks to stay and camp, as well as many free or cheap sites, this area of WA has very few of these facilities; comments on council camp-sites (......the lazy caretaker, dirty toilets...) or caravan parks, expensive and crowded does not help much. I normally use Camps Australia Wide and Wiki Camps as my guide but there are not many camps and comments of users on caravan parks are as usual, expensive, crowded, not friendly and you have to pay for some 50% of facilities you never use, a piece somewhat levelled surface of green grass and toilet are enough for us two.
Comments about personal experiences are welcome as well as links to find true information. We are 70.
Thanks in advance.
Carlo