As I understand it, the legal case is easy. The same law that underpins our right to garage a car at home applies to aircraft. Its a legal precedent that dates to the horse & buggy era. The problem is that there has never been a proper challenge, so instead there is the crazy dance between councils trying to apply made up local regulations and aircraft / helicopter owners wanting to avoid legal costs and being ostracised by neighbors.
Lindsay Fox overcame his difficulty using the pre-existing use clause. When a friend had similar problems he engaged the same lawyers to run the same argument and you've never seen a council back down faster.