<we always used to call our parents' friends Auntie Pam or Uncle Godfrey or whatever their names were.>

Yeah, that was my experience too. I had so many honorary aunts and uncles that I was well into my teens before I managed to sort out who was what.

Is this a common convention? I suspect so. Are there any interesting similar usages in places other than Indonesia and Oz? (I am afraid I have lost track of your familial origins, Bingley, although I think I read something somewhere here.)

Kindest rgds,
rhapsody lute, aka lusy