I like Guy, but what he’s done (or not done, maybe) is fairly wrong in my book! 180 on any public road is madness, and if he gets caught, it should be jail time.
I don’t think you could(or should) do 180 on open bits of the isle without getting a talking to from the plod. The limit is the limit, not the safe speed at which you can drive that section of road, and 180 is dangerous driving no matter if the road has a limit or not!
You don’t have a human right to drive a car, it a privilege, and one you have provided you’re trained adequately and follow the rules of the road (highway code). Regardless of how the limit was set, you have to follow it. Don’t and your in the wrong*! Simples!
(*try arguing in court that the limit was too low, and see where that gets you!)