Thanks folks. I was 6 when we left Montevideo; while there we made a number of visits to Carrasco Airport (our 2nd home was actually in Carrasco). I think my Dad was sometimes sent to the airport to greet and send off visiting VIPs. It usually meant a superb ice cream and coke in the cafe while watching all the planes. Pretty sure that I remember Caravelles, Viscounts and Vikings being there among all the US planes. Tail draggers had the greatest appeal to me.
I have been trying to remember seeing the propeller in the smallish tail-dragger we flew in. I think I remember being sat behind and to left of the central .pilot, and biggish windows rather than porthole types; This definitely suggests a Dragonfly or Rapide rather than a DC3.
Very grateful to all, I did not expect a single answer and replies have been great!