There may be another side of it: the tories do worse in cities better in the country.

BBC offices tend to be in cities so their staff are going to be surrounded by more lab/lib people meanwhile apart from debates where the audience is selected to match national statistics BBC studio audiences tend to be people who live in cities and are willing to stand in line for a long time for free tickets so are more likely to be young and poorer which makes them more likely to be lab/lib.