Starring Imelda Staunton. Rated PG

A slightly dour critique of modern Britain is hiding inside this feel-good comedy aimed at the Exotic Marigold crowd. And the filmmakers themselves don’t seem to know it’s there.

Director Richard Loncraine, veteran of much historical drama for U.K. television, assembled an ideal cast for this tale of late-life self-discovery. Diminutive Imelda Staunton headlines as stuffy Sandra, whose businessman husband, Mike (Scotland’s John Sessions), has just been knighted. But at the party announcing her ascension as “Lady Nevershits” (as one wag calls her), she discovers that Mike has been laying another lady.

The family lives in a massive country villa, but Sandra’s only option is to move in with her estranged older sister Bif (Celia Imrie) in a crumbling London housing project. Big sis is a playful bohemian still swinging (both ways) in her 60s, and pals around with unstiff-upper-lippers like pot-puffing Charlie (Timothy Spall) and Ted (David Hayman) and lawyer Jackie (woefully underused Joanna Lumley).

They all meet at a local dance class run by a spunky choreographer (Indra Ové). Turns out Sandra was quite the stepper in her day, although we initially don’t see much of that, given her current grumpiness. She gives a hard time to handyman Charlie, always fixing things at Bif’s place (but not Bif herself), so we know where that must be going. Obviously, Sandra will find her feet moving to a mambo beat—and you know how we all love to see oldies doing the Mashed Potato—but this sketchy subplot must compete with cancer, Alzheimer’s disease, and the viral whims of the interwebs.

Screenwriter-producers Meg Leonard and Nick Moorcroft, younger than their cast, failed to grasp that the film’s central pleasures would (and do) come from relaxed actorly interplay. Instead, we get problem-solving peregrinations and production numbers that feel unrelated to the story, even when they give it a reason to jump briefly to Rome. But, hey: free vacation!

Staunton’s character and hairstyle go through abrupt changes, and there’s little attempt to connect the subplots. There are some interesting and surprisingly vernacular commentaries about England’s changing class concepts and the starkness of postwar life, but these seem accidental. In any case, the movie never locates its own you-know-whats.