What are the first names of the foursome that are going out together?
Sitting in deckchairs and touring churches is not the holiday 17-year-old Richard wants, but his parents insist on taking him. They are staying at the Tregarron guesthouse in the (fictional) seaside town of Easton in Suffolk. This traditional English boarding house is owned and run by the formidable  Miss Wilbraham.   
On arrival, Richard befriends Edwin, who is girl-crazy and takes Richard under his wing. In search of girls, Richard and Edwin attend a beach service organized by the local church  youth group. After the type of evening one might expect at such a gathering, they enjoy a brief tryst with the twin daughters of the minister. 
The following evening another visitor, Julia, agrees to a date with Edwin but only on condition that Anna, her Dutch foreign exchange student friend, can join them. Edwin persuades Richard to join them to make up a foursome. Escaping from his parents on the pretence that the quartet is heading to the youth group's Sausage Sizzle, Richard and his friends visit a local jazz club instead. 
Anna attempts to sneak away with some local bikers and Richard gives chase. As Anna rides away on the back of one biker's machine, Richard jumps on the other. The bikes race off into the sand dunes; where Richard and Anna fall off the pillions and into each other's arms. Richard is annoyed but Anna finds the whole affair amusing. Reaching for a handkerchief to clean a cut on his head, Richard also pulls out a condom that he has taken from Edwin's room.
Julia and Edwin, meanwhile, have been to fetch help. Julia's father, Richard's parents and the minister from the youth group set off to rescue Richard and Anna. A lady walking her dog along the beach stumbles across Richard and Anna as it becomes clear that Richard has experienced sexual initiation. The parents and the minister round the corner just in time to catch the teenagers in flagrante delicto.
Both families make excuses to end their holidays early and head for home.
Julia Edwin Anna Richard