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

Me too. It took me years to work out the real ones from the imaginary ones. The imaginary ones were always so much more fun. I've explained that to my children as they are sadly lacking in the aunt and uncle department. Fortunately my friends ahve been very happy to fill in the gaps (especially at Christmas and birthdays) but I think the practice of calling them uncles and aunts had fallen out of favour. I think we should have a new term for honoured family friend. We have a good collection of god-parents and have added quite a few honorary godparents to the list (it gets a bit tricky explaining the range of religions and un-religions involved), perhaps Aunt and Uncles would have been simpler.