Avis attended Manley Park Municipal School and Chorlton Central School in Manchester. She formerly worked as a secretary and nursery teacher before deciding to switch careers and become an actress. She gained stage experience in rep and made her first professional appearance at Chorlton Rep Theatre in Manchester in 1947. Her first London appearance was with the Theatre Workshop Company in 1952. She returned to that company many times during her long career. In addition, she acted in other productions in Zurich, Moscow and America. Her theatre work included 'An Enemy of the People', 'The Good Soldier Schweik','Mother Courage', 'The Italian Straw Hat', 'Captain Brassbound's Conversation', 'The Playboy of the Western World', 'A Taste of Honey', 'The Hostage', 'Ned Kelly', 'Fings Ain't Wot They Use T'Be', 'Henry VI', 'Fiddler on the Roof', 'Sweeney Todd', 'The Rivals', 'Billy' and the title role of Marie Lloyd in 'The Marie Lloyd Story'. Avis was married to Derek Orchard.