Langford attended The Arts Educational School and the Italia Conti Academy stage school. Her first stage appearance was at four months and her first public appearance was at 15 months when she danced in specially made ballet shoes. She first came to public attention when, aged 6, she won the talent show Opportunity Knocks. This led to early fame in the television series Just William, the 1976 film Bugsy Malone and the 1977 film Wombling Free. At this time, she was associated with fellow child star Lena Zavaroni.
Between 1986 and 1987 Langford played the role of Mel, companion to both the Sixth and Seventh Doctors in the BBC1 series Doctor Who.
Langford and Evers appeared again on the programme in the one-off Champion of Champions show which followed series two. They were scored second overall by the judging panel but again the public vote was less favourable and they were amongst the four teams eliminated in the first round of the competition. Langford then toured with Torvill & Dean's Dancing On Ice Live in 2007, a series of 42 shows in which she was the winner 27 times.
Dancing On Ice has sparked a regeneration in her career. She returned to the West End theatre in April 2006 (for the first time since 1998) playing the murderess Roxie Hart in the long-running West End musical Chicago and again in Dec 2007-Feb 2008 in the same role, also in 2006-7 she appeared in the Birmingham and Plymouth tours of Guys & Dolls playing Miss Adelaide Adams, a dance hall hostess. Starting in 2006 she has also been touring with Sandi Toksvig in a two-woman theatrical show called Short and Curly
She has also made a number of guest appearances on television, including Agatha Christie's 'Miss Marple' on ITV (playing Betty Johnson alongside Brian Conley in the episode By the pricking of my thumbs, February 2006), The Catherine Tate Show (late 2006), Supermarket Sweep with Dale Winton (February 2007) and the children's programme Hider in the House (March 2007).
In July 2007 she was a judge on the ITV series Baby Ballroom: The Championship. Starting on 16 February 2008, Bonnie was 1 of 5 celebrities making up team Ant for there new team game Ant versus Dec in Ant & Dec's Saturday Night Takeaway.She survived right up until the final edition, reaching the semi final stage & just missing out on the final which was eventually won by team Dec.