Marking an improbable union between writer-director Dan Mazur (“Borat,” “Bruno”) and producers Tim Bevan and Eric Fellner (“Notting Hill,” “Bridget Jones’s Diary”), the frequently funny “I Give It a Year” strikes a welcome balance between the vulgar talents of the former and the dependable formula of the latter without ever fully subverting the expectations of a modern rom-com.

After seeing Nat (Rose Byrne) and Josh (Rafe Spall) on their wedding day a mere seven months after they first meet, we soon jump ahead by nine months to realize that wedded bliss isn’t all it’s cracked up to be. He’s a bit of a layabout, she’s something of a workaholic, and each is tempted by the arrival of seemingly better-suited Americans -- for Nat, it’s new client Guy (Simon Baker); for Josh, old flame Chloe (Anna Faris).

The familiar Working Title tropes are all there: extramarital temptation, a wintry London setting, the crass best bud (Stephen Merchant, quite the cad in his few scenes). Mazur isn’t interested in reinventing the wheel, but instead giving it a cynical spin -- more hangover bile than honeymoon glow -- and keeping it well-oiled with vulgar laughs. Try as they might to ground Nat and Josh’s relationship in something resembling real emotional stakes, Byrne and Spall are better off as serviceable straight men to their consistently funny compatriots (although their drawn-out discussion of resuscitation scenarios and repeatedly uneasy family interactions do earn some chuckles).

If the scene-stealer isn’t Merchant’s heedlessly offensive jerk, then it’s Olivia Colman as a deeply bitter marriage counselor, or Minnie Driver and Jason Flemyng as a similarly spiteful couple. Baker has some fun as a suave suitor who knows exactly how rich, handsome and charming he is, and just when it seems that Faris’ comedic chops have been marginalized entirely, she gets to participate in a pricelessly humiliating three-way sex scene.

Cinematographer Ben Davis ensures that the film’s look matches those of other Working Title favorites, and the soundtrack is laden with soft covers of pop standards. The beats and trappings are all standard-issue, but the gags are funny enough, often enough, to offset such routine proceedings. For those as cynical about rom-coms as yours truly and Mazur seem to be, the ending will come as a riotous reversal of expectations while simultaneously satisfying those keen on happy endings. Although it may not ultimately prove crafty enough to serve as the chick-flick equivalent to “The Cabin in the Woods,” “Year” still manages to have its wedding cake and spit on it too.

Grade: B