Torbanlea Racecourse - Good open flat area, Limit of stay - 7 days. (Though if you go away for a couple of days you can return). Caretaker lives in on site van (not always there as he also works). Cost - $5/night (just to park up there with use of flush toilets); $10/night (gives you a key to use hot showers); $15/night (gives you all of the above plus power). No need to prebook. Photo of area looks nice and clean area.
