According to Wikipedia: "Dashes have been cited as being treated differently in the US and the UK, with the former preferring the use of an em dash with no addi

According to Wikipedia: "Dashes have been cited as being treated differently in the US and the UK, with the former preferring the use of an em dash with no additional spacing and the latter preferring a spaced en dash." Though I prefer the spaced en dash myself, and I am in the UK, I think there's probably a lot of variation on both sides of the Atlantic.