House to Let is the 16th episode in the series.
When Paul buys a recently-vacated house in the close as an investment, Martin is concerned as to what his tenants will be like. However in the persons of Dan and Diana Danby, Martin has found his ideal new best friends, a dull couple into jam-making and being in bed by nine thirty at night. Then comes the down side - Dan has a habit of obsessing with people he likes to the point of pursuing them everywhere, which why they had to move. And Martin is the latest object of Dan's fixation.