whether I should have said 'bring' or 'take' when I duly informed my spouse depended on whether I (1) intended to wait in the customer lounge [not longue] so that I wouldn't have to come back, or (2) arranged for other transportation and left my car there for the interim.

Not necessarily (to my mind). The usage, appears to depend on, WHO one is talking with.

Three people: Ann, Bob (Ann's husband) and Jo (mechanic).
Ann - Bob: I am takingthe car to the mechanic.
Ann - Jo: I am bringing the car in.
(If Bob decides to meet Ann at the mechanic's place and give her a ride back home..)
Ann - Bob: I shall bring the car in to Jo's at five and meet you there.

As I understand, whilst using bring, there must be a one on one communication between people, one of whom at the very least (either speaker or addressee), is at the location that bring is moving 'towards'. Whether we choose to use bring, or, take, is fluid, dependant on the speaker/ addressee perspective.