Just when I’m ready to write off the mockumentary as an exhausted form, along comes this delightful and hilarious improv comedy from the UK in which a bridal magazine sets up a promotional contest for the best offbeat wedding. The three finalist couples are thematically committed to tennis, musical comedy, and nudism, and a gay couple is assigned to guide them through their nuptial ceremonies. Director Debbie Isitt falters when she tries to shoot an elaborate production number but triumphs in her cast’s quirky characterizations and the ensuing complications and contradictions (e.g., “Please get it into your thick head how much I respect you”). With Vincent Franklin, Jason Watkins, Stephen Mangan, Meredith MacNeill, Martin Freeman, Jessica Stevenson, Robert Webb, and Olivia Colman. R, 94 min.