The petrol station attendant in the first scene is played by Hamza Jeetooa, who appeared in an episode of the BBC sitcom 'The Thick of It', as Raj. David Dawson, who plays Toby Kent in this series, also appeared in 'The Thick of It' as Emma and Phil's flatmate, 'Affers'.
When Luther returns home to his flat at the end of the episode, we see him go to the 21st floor. This could be homage to Sherlock Holmes who lives in 221B Baker Street.