Northern or Southern summer 1959 ? The BOAC services down to South America had not started until 25 January 1960, having been previously given up in the early 1950s. Regarding Aerolineas, although operating to London with Comets in 1959 (a pioneer in their own right) they appear never to have stopped at Montevideo on these services in the Comet era, you would need to have gone across to BA to use the service.
http://www.timetableimages.com/ttima...r59/ar59-2.jpg