On a sweltering summer weekend, Andy, a senior chef at a bustling London catering company, makes an impulsive decision to purchase a rundown fast-food van from a dubious acquaintance named Patsy. With dreams of revitalizing the van for a local fast-food business, Andy's excitement is met with skepticism by his sensible and good-natured wife, Wendy. Despite her doubts, she supports her husband's ambition. Their twin daughters, 22-year-olds Natalie and Nicola, exhibit contrasting reactions: tomboyish Natalie embraces the notion that it might bring her father joy, while the bitter and withdrawn Nicola scornfully labels Andy a "Capitalist!"
As night falls, a troubled Nicola indulges in binge eating, devouring chocolate and snacks before inducing vomiting. Unbeknownst to her, Natalie, who is awake nearby perusing US travel brochures, hears her sister’s distressing behavior, hinting at a shared family crisis.
In the meantime, family friend Aubrey (Timothy Spall) is committed to opening a Parisian-themed restaurant called The Regret Rien. Wendy, looking to assist, takes on a part-time role as a waitress. However, her and Andy's initial enthusiasm quickly dims as they confront Aubrey's chaotic décor—a hodgepodge of outdated French kitsch mixed with garish Victorian accents—and his bizarrely unappetizing menu. The offerings include unusual combinations like saveloy on lychees and liver in lager that challenge even the most adventurous palate.
During the day, Nicola’s secret romance takes place in the family home, revealing her complex and troubled relationship with intimacy. Her lover, struggling to connect with her emotionally, ultimately departs, leaving Nicola in a further spiral of despair.
The grand opening of The Regret Rien turns into a fiasco when Wendy discovers Aubrey neglected to promote the event, resulting in a complete lack of patrons. Aubrey, overwhelmed, succumbs to inebriation, prompting Wendy to take charge and manage not only him but his disheartened sous-chef, Paula.
Meanwhile, Andy, lured by the local pub scene, drinks excessively alongside Patsy and winds up spending the night in the decrepit fast-food van parked in the driveway. Upon discovering him there later, Wendy gets riled up, revealing the mounting frustration she harbors towards her family's chaotic dynamics.
Amidst this turmoil, Natalie finds solace in her work as a plumber, enjoying the simplicity of life, while Nicola's isolation deepens, leading to a much-needed confrontation with Wendy. In this cathartic discussion, Wendy conveys her genuine concern for Nicola’s well-being, recounting the sacrifices she and Andy made for their family, including Wendy's abandonment of college and Andy's uninspired job. The tension culminates when Wendy heartbreakingly expresses, “We don’t hate you! We love you, you stupid girl!” leaving Nicola to grapple with her emotions.
The narrative progresses as Andy manages his bustling kitchen with vigor, but after slipping on a spoon and injuring his ankle, Wendy aids him in recuperation at home. Together with Natalie, they bring comfort to Andy, and Wendy finds time to mend her relationship with Nicola.
The film concludes on a hopeful note with Natalie and Nicola sharing a tranquil moment together in their garden under the evening sun. Natalie encourages Nicola to confess her struggles to their parents, offering her a glimmer of support by asking, "D'you want some money?" to which Nicola gratefully accepts, marking a turning point in her journey towards recovery.
