Although I suspect.. with the "no trailer for more than 30 days" Bull.. that their planning act says no "accessory" buildings prior to a main dwelling/residence. As long as you've done nothing to be under planning control they can't stop you from building less than 10 square metres... as it doesn't fall under the building act, as long as there is no plumbing inside said structure. Outhouse and camp kitchen under a tent awning.