This is the "International Wife Swapping Sketch". The "Una" refered to is the name of Mr Johnson's wife (Una is a name not much used in UK anymore - its considered a bit dated.)
P.S. It isn't Michael Palin who makes the announcement, its a guy called Frank Bough who was (and still is) a famous UK presenter. At the time of filming Monty Python he was the presenter of the sports programme Grandstand.
Cardinal Fang's Python Site
Reply address is NEVER CHECKED. Contact me at "latinum" at "hotmail" dot "com".