Charlotte is the half-sister of the writer John Le Carré (whose real name is David Cornwell), of whom she says "He's the best brother a girl could have".

Their father Ronnie Cornwell (1906-75) was married at least three times and has been described as "an epic con man of little education, immense charm, extravagant tastes, and no scruples". Ronnie was a larger-than-life character who ran race-horse scams, sold make-believe businesses and ghost properties, swindled insurance companies, was known for impersonating people and running away from debts, and generally had a huge talent for financial disasters and betrayals. He stood for parliament to avoid being called up during the Second World War. Altogether, he created a dysfunctional life for his four children which they both survived.

Charlotte has one daughter, Nancy Cranham ("the sunshine of my life"), from her relationship with the actor Kenneth Cranham. Nancy is now a student at London University, reading for a degree in History.

After drama school at the end of the 1960s (the Webber Douglas Academy of Dramatic Art in London), Charlotte was in rep at the Bristol Old Vic for three and a half years, before being launched into stardom by the television series Rock Follies. After the second series of that, she went on to join the Royal Shakespeare Company, and worked in theatre as a leading actress (for the RSC, the National Theatre and in London's West End) on and off through the '80s and '90s. In 1998, she set up an organization called Greyhounds UK, which aims to give a happy retirement to discarded racing greyhounds.

After the BBC film Care (2000), Charlotte abruptly handed her flat in London over to her daughter and moved to California, explaining that she wanted an adventure to launch her into the next part of her life. She has taken several parts in Hollywood shows and also now does some teaching, under the umbrella of her own small business based in Los Angeles, called Fearless Choices.