The UK Polaris submarines were built at Barrow-in-Furness and based at Clyde Naval Base; they were never located at Newcastle or indeed, in the Northeast.
In the missing girl's dorm room, Bachus picks up a paperback copy of "The Medium Is the Massage," which was published in 1967, but the title card in the beginning of the episode states that it's taking place in 1966.
When Gently and Bacchus visit the Seagull Club, the incidental background music is an instrumental cover of Procol Harum's "A Whiter Shade of Pale." However, the action is set in 1966 as the opening titles show, and the song was not recorded until April 1967 & released May 1967.