Così fan tutteEnglish national opera, london coliseum Greeted at the door by fairground barkers, you understand this staging of Mozart’s 1790 opera isn’t going to be a searing social critique. But a likeable production by Phelim McDermott’s theatre company Improbable at least reminds us that Così is a comedy – rather obscured lately in a welter of earnestness; modern opera tends to obsess on traumas that robust ­eighteenth-century types would simply have got over.The chosen set-up is 1950s Coney Island, and McDermott wheels on a somewhat tangential circus freak show, handy for shifting the furniture between swallowing swords and whatnot. There aren’t too many other ideas, so it’s nice to have something to look at; no doubt this was bo