Toby Jones is too short to have been in the police force in 1975. He is 5 foot 4 inches but the height requirement was at least 5 foot 8 inches.
At 14 mins 40 seconds, Tina Charles' "I Love to Love" is played, but this didn't come out until January 1976. This episode was set in October 1975.
When the police are on stakeout near the spot Emily Jackson is working in January 1975 they stop the Land Rover using a Rover SD1 with an "S" suffix plate. The "S" suffix dates the car to between August 1977 and July 1978, the SD1 itself wasn't launched until June 1976, nearly 18 months after the events portrayed took place.