At 20:01 when Maddy suggests opening a grave, Jonathan replies "Thank you, Dr. Van Helsing." Van Helsing was a vampire hunter in the Dracula canon.
The "Josef K" mentioned by Jonathon is the protagonist in Franz Kafka's "The Trial."
At 3:45 the DI refers to "WPC Hicks." DI is Detective Inspector; WPC Is Woman Police Constable. The term WPC was officially discontinued in the UK the year after this episode was transmitted.