The Kipper and the Corpse (a.k.a. Death) - S2-E4
Visible crew/equipment: In the kitchen scene with Basil, Sybil and chef, Basil says, "Would you believe it, I give him his breakfast, I take it all the way upstairs." At this point, the shadow of a boom microphone on the wall to the right is visible.
The Kipper and the Corpse (a.k.a. Death) - S2-E4
Visible crew/equipment: When Mr. White asks if Basil can clean their room later the boom mike shadow is visible on the door behind Mr. White.
The Kipper and the Corpse (a.k.a. Death) - S2-E4
Visible crew/equipment: When they discover that Ms. Tibbs has fainted in the office the boom mike shadow is visible on the wall to the right.
The Kipper and the Corpse (a.k.a. Death) - S2-E4
Visible crew/equipment: When Polly is on the phone with the undertaker and she says "I'm afraid somebody's died tonight", the boom mike is visible to the right of the screen.
The Kipper and the Corpse (a.k.a. Death) - S2-E4
Visible crew/equipment: When Basil, Manuel and Sybil enter the office and find Miss Tibbs fainted next to the corpse, the boom mic appears on the righthand side of the screen next to the fan on the wall. And when the camera switches back to the full shot of all the characters, the boom mic appears again.
The Kipper and the Corpse (a.k.a. Death) - S2-E4
Visible crew/equipment: When Dr. Price asks who found the dead guest the boom mike is visible above him.
Answer: It's "Leisure Complex" by Dave Gold and Gordon Rees. Can be found on YouTube. The relevant clip is around 25 seconds in.