The thing that's shit about this is that while the w3w website acknowledges you might have misheard and offers alternate suggestions, it only ever offers two of them, neither of which are correct.
If it were designed to be properly useful, it would offer a long list of all plausible alternatives, but of course that would be embarrassing because there are probably hundreds, so marketing wins over usefulness*.
And if it were a proper standard and not stupid rent-seeking, someone else could build a website that does this.
(* I'd like to think the emergency service integrations aren't so limited, but that's wishful thinking, isn't it?)