no development of any kind can be attempted within 30 miles of the site itself
It would seem nobody has told East Devon District Council this, since they're currently planning a new town of 40000 houses only seven miles from the Jurassic Coast! It would also come as rather a surprise to the many other smaller-scale developers currently building along this busy coastal strip.
Well, that's the situation in Utah. The UN attempted to designate the site, the state and property owners sued, the Fed'ral Gubbmnint under Clinton stepped in, injunctions flew fast and furious, and the thing is still tied up in Federal Courts. And will be for years to come.