The Germans - S1-E6
Other mistake: When Basil shuts Manuel in the burning kitchen and slams the door, the walls shake.
The Builders - S1-E2
Other mistake: In the end credits, Major Gowen's surname is incorrectly spelled "Gowan."
Other mistake: Dinner is said to be at 9:00 pm, with guests arriving at 8:00-ish for cocktails. But the 2 old ladies come downstairs, and say "good morning." Then, the Major goes out to play golf. Finally, Basil's wife and Audrey go out for golf. Is it morning, afternoon, or night?
Answer: It's "Leisure Complex" by Dave Gold and Gordon Rees. Can be found on YouTube. The relevant clip is around 25 seconds in.