It’s 2014, and aspiring indie-rock band Dive Bella Dive are cold, tired and suffering from the effects of sustained consumption of drink and drugs.

Their Ealing residence is falling apart at the seams, and they’re about to be dropped by Island Records. Their debut album, recorded in Los Angeles at the behest of super producer RedOne, who was bewitched by their rock star looks, will never be released. Their career is over.

Four years later, that band’s frontman, Barns Courtney, ...