In the planetarium, Hathaway points out the constellation of Leo, "laying right smack in between Cancer in the east and Virgo in the west..." But the reverse is true: Cancer is actually WEST of Leo, and Virgo is EAST.
Professor Garwood says that an astronomical unit cubed is equal to G, times the mass of the Sun, times a year squared, times 4 pi squared. It is in fact equal to G, times the mass of the Sun, times a year squared, divided by 4 pi squared. The value given in the show is too big by a factor of 16 pi^4 (~1558.55).
Inspector Lewis refers to "East Sussex Police," but there hasn't been an East Sussex police force since 1968. It's simply Sussex Police.
The college gardener is using a rotary lawn mover to leave stripes in the grass. This would require a cylinder lawn mower.
Lewis gets a hot dish out of the oven with a cloth but when serving it up holds it with his bare hand to steady it.