"Up above Grab wrote "no-one", I believe I've seen it written by UKers as 'noone' and in the US we spell it 'no one'."

"No-one" has become quite common in the US; I believe it's the standard spelling used in the New Yorker, for example. "Noone" is positively barbaric.

I can't for the life of me imagine why anyone, including the proofreaders at the New Yorker, would feel the need to alter the perfectly sensible and unambiguous "no one".