Room 13 by Robert Swindells.
Room 13 (1989) by Robert Swindells is a genuinely frightening story about vampires and a school trip to Whitby — the town associated with Dracula.
Fliss and her class go on a school trip to Whitby, North Yorkshire — famous for its Gothic abbey and its connection to Bram Stoker's Dracula. They stay in a guest house with twelve numbered rooms on one corridor. But Fliss notices that the rooms go straight from 12 to 14 — there is no Room 13.
One of the girls, Ellie-May, begins to change after the first night. She becomes pale, listless and strange. She is slipping away at night — to Room 13, which only exists between midnight and 3am. Inside is a vampire named Elijah — who has been sleeping for a century and is now awakening.
Fliss discovers the truth and, with her friend Gary, races to save Ellie-May and destroy the vampire before anyone is permanently harmed. The climax takes place in Whitby's famous graveyard overlooking the abbey. The vampire is defeated.