The ever-glamorous and self-indulgent Edina and Patsy are now in their 60s, and Edina is still running her PR agency, which is quickly running out of money and interest. The duo realise that Edina needs a miracle to save her PR company and renew her reputation.

Bubble wakes up a hungover Edina, who has come home from a fashion event. Edina realises that she signs a deal for an autobiography that day. Edina wakes Patsy up and tells her about her book, and how it will be "made into a film because it's about her life", whilst Patsy self-applies Botox. The company head (Mark Gatiss) rejects Edina's book because it is lazily written and there is little interest in Edina's PR agency. While Patsy is setting up designer Huki Muki's fashion event, Patsy learns that supermodel Kate Moss is changing her PR, and immediately informs Edina. Patsy phones whilst Edina is at a PR meeting with rival PR Claudia Bing (Celia Imrie) and during the phone call with Patsy she accidentally leaves her phone on "speaker" and Claudia learns that Kate Moss needs a new PR.

Edina and Patsy go to the fashion event with Edina's granddaughter Lola while Saffron "Saffy" Monsoon, Edina's daughter and Lola's mother, has a night out with her new boyfriend Nick (Robert Webb). Edina finds Kate Moss on the balcony overlooking the Thames. As she moves to speak to her, she notices that Claudia is also heading for her. Rushing to get to Kate first, Edina accidentally bumps into her and she falls off the balcony and into the river. Among the witnesses is Lulu, who is already at odds with Edina over missed singing engagements.

Hysteria pervades the event as Kate is presumed dead. The media immediately storms the scene to report her disappearance and assumed death. Edina and Patsy, along with Lola, are taken into police custody. Saffy arrives to see them and make sure Lola is all right in company with Nick, who is revealed to be a police detective.

Edina returns home the next day. Patsy arrives angry; she's been fired from her job because of her association with Edina and the previous night's events. The pair make up and return to the Thames to look for Kate, using Bubble with a flashing beacon upon her head to simulate and retrace how Moss may have been carried away, but the beacon comes loose and unable to find Bubble, they presume her dead, too. They decide to flee before the media firestorm gets worse, taking Lola and her credit card along. The three land in Cannes while Saffy desperately searches for Lola or clues to her whereabouts back in London, finally consulting Christopher (Chris Colfer), Edina's friend and stylist.

In Cannes, Edina and Patsy call upon Patsy's ex-lover, billionaire Charlie (Barry Humphries). After Charlie rejects them, they seek help from Edina's mother (June Whitfield), who is celebrating her cousin Violet's birthday. During this party, they encounter the Richest Woman in the World. To attract the Woman and get quick money, Patsy quickly changes her identity to a male alter-ego, "Pat" Stone. The following day, Patsy marries the Rich Woman and Edina and Patsy find the wealth they were looking for as they stay in a high-class hotel with Dame Joan Collins and Dame Edna Everage as fellow guests.

Meanwhile, Edina and Patsy are seen in public by Emma Bunton who tells Lulu about their whereabouts. Saffy arrives in Cannes with Nick and immediately heads to the hotel to find Lola. Lola is with Emma who tells Saffy of Edina's whereabouts, even though it is the least of Saffy's concerns. Lulu flies out to Cannes and meets with Bubble, who reveals that Kate just swam off and did not drown in the Thames. Bubble also reveals that she is also a millionaire and owns a massive Cannes pavilion because she has had control of Edina's accounts for years, and has been embezzling from the company.

Lulu reports Edina and Patsy's whereabouts to the police, since her only desire is to destroy Edina for what she has done. The police find Edina and Patsy and chase them through the town, the duo escaping in a small three-wheeled fish-market van. As they reach Bubble's pavilion, the van's brakes fail and they roll backwards and fall into an infinity pool attached to Bubble's house. Saffy arrives at the scene to find Edina and Patsy slowly sinking into the pool, still inside the van. Edina apologises to Saffy for being a careless mother and wishes to drown in the pool, and to finally embrace the fact that she is old and can't run from justice forever. Saffy tells her that she loves her. Bubble reveals that Kate Moss didn't drown in the Thames, and Edina immediately exits the van, realizing she's innocent.

A montage plays of countries celebrating that Kate Moss is still alive and that Edina is her new PR. Edina's PR agency is renewed, and Kate is in even more demand now that she has been found. The film finishes with Patsy revealing to her rich wife that she isn't actually a man called "Pat" and is really a woman. Her wife reveals that she is actually a man and the film closes with the series's popular theme song, "This Wheel's on Fire" sung by Kylie Minogue.