Her training took place at East 15 Acting School, London. She has appeared in many television roles including Bergerac (1981–1984), 2point4 Children, Making Out, Summer Hill, Lace, Jackanory, Archer's Goon, The Demon Headmaster, A Little Princess, The Worst Witch, The Queen's Nose and Coronation Street, as well as an early appearance in series one of the Hale & Pace show in a number of sketches. In 1989, Badland also appeared in "The Rough and The Smooth", an episode of All Creatures Great and Small. She played the recurring villain Blon Fel-Fotch Pasameer-Day Slitheen a.k.a. "Margaret Blaine" in the 2005 series of Doctor Who. She also provides commentary on the Doctor Who Complete Series One Box Set, on the episodes "World War Three" and "Boom Town" as a Slitheen. In 2006 she put in an appearance at Larkhall Prison for the eighth series of ITV1 drama Bad Girls. She played Angela Robbins, a disturbing inmate who was suffering from Dissociative Identity Disorder.
She has also appeared in many films including Jabberwocky (1977), Out of Order (1987), Beyond Bedlam (1994), Captives (1994), The Grotesque (1995), Little Voice (1998), Beautiful People (1999), Honest (2000), and Charlie and the Chocolate Factory (2005), and appeared in the TV adaptations of Gulliver's Travels (1996) as the farmer's wife, and A Christmas Carol (1999) as Mrs Fezziwig. Badland has performed in several radio dramas including BBC Radio 4's Rolling Home (2001), Smelling of Roses (2003) and an adaptation of George MacDonald's novel At the Back of the North Wind; lead role as DC Gwen Danbury in An Odd Body on BBC Radio 4 Extra. In 2005 she took over the role of Hazel Woolley, the "bad seed" adopted daughter of Jack Woolley in the long-running radio soap opera The Archers, and in 2008 appeared in the radio serial The Way We Live Right Now as Tilly Carbury.
Badland was also the presenter of BBC's You and Me in the early 1990s and appeared in the British comedy Three and Out released on 25 April 2008. She also played the sharply conservative Ethel Tonks in the BBC's All the Small Things (April/May 2009) alongside Sarah Lancashire, Neil Pearson, Sarah Alexander and Bryan Dick. In 2009 she appeared in Casualty as a disturbed mother who was always worrying about her daughters.
On 5 July 2010 she appeared as a Verger in Doctors. In 2012, Badland appeared as Ursula in the new CBBC science fiction series, Wizards vs Aliens. She was also in BBC's Cutting It, for 4 series.
In the CBBC hit show The Sparticle Mystery, Badland played DoomsDay Dora and HoloDora. She appeared in four episodes as DoomsDay Dora and eight episodes as HoloDora.
On 12 December 2013, it was announced that Badland would appear as a regular in the BBC soap opera, EastEnders, playing Babe Smith. She made her first on-screen appearance in the episode broadcast on 31 January 2014. On 18 September 2016, it was announced that Badland had been axed from the serial by new executive producer, Sean O'Connor, with the character making her final appearance on 9 February 2017.
She will also be appearing in the 6th Series of the Tracy Beaker Spin-Off The Dumping Ground at some point during 2018.
Badland has had a wide-ranging stage career, including seasons with the RSC (her Audrey in As You Like It, 1973, was an auspicious debut in a leading company) and the Young Vic. Her first professional productions were in director Noel Willman's Three Arrows (by Iris Murdoch) and Richard Cottrell's Ruling the Roost (Georges Feydeau) at the Cambridge Arts Theatre in October 1972.