Was it a Vanden Plas Princess (like the one parked nearby and that we all admired)?
It was more probably a Rover that father and you set out to buy that day.

 I've been in love with C1s since the age of 4 or 5, when I followed my father to buy a savanna beige Audi 100 LS, [also] from 1974
http://autos.groups.yahoo.com/group/audi100c1series/