When Mr. Harmon adjusts the talking mannequin of Mr. Grace, he does so by twirling his screwdriver in the statue's ear. This causes it to raise its arm and tip its hat, lifting the entire head in the air. However, if the head was completely detached from the body, inserting a screwdriver in the ear couldn't possibly cause the body to behave differently.
When Mrs Slocombe confiscates Ms Brahms' padded bra, a couple is seen walking up the stairs to an open lift. The man trips at the foot of the lift and you can hear this occur.