The film opens with pub landlord and frequent holidaymaker Vic Flange (Sid James) openly flirting with the much-married saucepot, Sadie Tompkins (Barbara Windsor) as his battleaxe wife, Cora (Joan Sims), looks on with disdain. Their twitching friend, Harry (Jack Douglas) arrives and lets slip that the package holiday Vic has booked to the Mediterranean island Els Bels (a pun on the slang expression "Hell's Bells") also includes Sadie, much to Cora's outrage. Cora, who avoids holidays because she hates flying, suddenly decides to accompany her boorish husband on the trip, to ensure he keeps away from Sadie.
The next day, the nasally Stuart Farquhar (Kenneth Williams), the representative of Wundatours, and his seductive assistant, Moira Plunkett (Gail Grainger), welcome the motley passengers. Among them the hen-pecked and love-starved Stanley Blunt (Kenneth Connor) and his prudish, overbearing wife, Evelyn (June Whitfield); a drunken, bowler-hatted mummy's boy, Eustace Tuttle (Charles Hawttrey); brash Scotsman, Bert Conway (Jimmy Logan); the young and beautiful Marge and Lily (Sally Geeson) and (Carol Hawkins); and Brother Bernard (Bernard Bresslaw), a young monk who has difficutly fitting into his new path of life.
Unfortunately, the hotel they are to stay in isn't finished as the builders have recently abandoned their jobs half-way through. Distraught manager Pepe (Peter Butterworth) desperately tries to run the place in a myriad of different guises and his shrewish wife, Floella (Hattie Jacques), struggles with the temperamental stove, whilst their Lothario son, Georgio, lazes about behind the bar.
The hotel also hides an assortment of tricks and Pepe is soon overrun with complaints, when Vic discovers Sadie naked in his shower, sand pours out of Moira's taps and the lavatory drenches Bert. Although agreeing to play leapfrog with Tuttle, Lily and Marge have their eyes on other things. Marge takes a shine to Brother Bernard, while Lily lures the dashing Nicholas (David Kernan) away from his jealous (implied) gay friend, Robin (John Clive). While most of the party go off to the village and get arrested for causing a scene at the establishment of Madame Fifi (Olga Lowe). Evelyn is left behind and seduced by Georgio, thus abandoning her frigid ways and resuming her sex life with Stanley. With the last-night bash swinging thanks to a local mixture that blesses the drinker with x-ray vision, the party goes with a bang as the hotel collapses. But all's well that ends well, when the holidaymakers reunite at Vic and Cora's pub.