Late last month in Glasgow, child fans of Roald Dahl — and their paying parents — were treated to something called Willy’s Chocolate Experience. They did not have a good time. Instead of an immersive dive into a world thrice turned into popular movies, they got a spartan warehouse, miserable-looking performers, and barely any candy. Who would foist this upon kids? His name is Billy Coull, and he’d like very much if everyone knows he didn’t mean to upset (or at least amuse) everyone.