By 1959 she was appearing with Kenneth Williams in the comedy revue Pieces of Eight, written by Harold Pinter and Peter Cook.
She had occasional guest appearances in television programmes such as The Avengers (after being passed over as Patrick Macnee's regular partner in favour of Honor Blackman) and in Danger Man. She appeared in two of the Carry On films and three of the Doctor films (e.g. Doctor in Clover). She interspersed these with performances in plays by Ibsen, Shakespeare and Henry James, reputedly keeping an edition of Plato's writings by her bed.
Fielding was the uncredited voice of The Village's announcements in The Prisoner, and co-starred with Tom Poston and Robert Morley in the 1963 version of The Old Dark House. In Dougal and the Blue Cat, based on The Magic Roundabout, she voiced the character of the Blue Voice — referred to as "Madam" by both Buxton (the blue cat of the title) and Dougal at various stages throughout the film. In the late 1960s, she was approached by Federico Fellini to work on one of his movies, but turned it down because she was already booked to perform on stage at Chichester Theatre.
She starred as a guest on The Morecambe and Wise Show four times between 1969 and 1972. In the theatre, she was in, among other things, Alan Ayckbourn's Absurd Person Singular at the Criterion Theatre, London, directed by Sam Walters, in 1974, and Fallen Angels at Watford, directed by Kim Grant.
As at 9 January 2011, Fielding is due to appear, from 14 to 19 February 2011, at the Jermyn Street Theatre, London in an English Chamber Theatre presentation of Jane McCulloch's Dearest Nancy, Darling Evelyn, the dramatised letters of Nancy Mitford and Evelyn Waugh.
Late in life, Fielding worked with writer-performer Graham Roos performing the role of Sandalphon in Roos' verse cabaret Apocalypse Calypso at King's Place.and most recently provided a substantial cameo in his film about Byron - Darkness.