Bastedo was born in Hove, England. According to her official website, her mother was of French, German and Italian descent. Her Canadian-born father was of Spanish, Dutch, Scottish and native Indian extraction. She attended Brighton and Hove High School and Brighton School of Drama.
She made her film debut as one of the title characters in William Castle's poorly received 13 Frightened Girls (1963). Bastedo received notice on the European continent, earning her the nickname, "La Bastedo". Although most familiar to viewers of 1960s TV, she was also known for her multilingual skills, speaking Italian, Spanish, French and German. This skill brought her to the door of 10 Downing Street to assist with translations and landed her the role of co-presenter of Miss World competitions with Peter Marshall in the 1980s. In 1979 she also played in the series The Aphrodite Inheritance. In 1988, Bastedo was the cover star for 'Rank', a live album by British band The Smiths that charted at number 2 on the British Album charts. In 1991, she appeared in a notable production of the psychological thriller Dangerous Obsession by N. J. Crisp, opposite Marc Sinden and John Challis, at the Mill at Sonning. In 1992 she appeared in "Fat" — the second ever broadcast episode of Absolutely Fabulous, playing a 1960s model associate of Edina and Patsy. Also seen in The Saint alongside Roger Moore, who later became James Bond 007.
In 2006, Bastedo was reunited for the first time with her co-stars from The Champions to provide commentaries and an interview for a DVD release of the show. Still working as an actress, she appeared in Batman Begins, and touring theatres in 2006 with a production of Beyond Reasonable Doubt alongside Leslie Grantham and Simon Ward. In 2008, she joined the cast of EastEnders, playing Cynthia. In January 2008, she appeared as co-presenter (with Ed Stewart) of "The Magic of Mantovani" at Lighthouse, Poole. The success of this concert led, the following year, to a second concert at Lighthouse in Poole, with the Mantovani Orchestra, which she again co-presented.
She dated David Frost and Omar Sharif but turned down the advances of Steve McQueen who, she recalled, propositioned her with the line, "My wife doesn’t understand me". In the case of Sharif the liaison lasted only a few weeks because of the actor's bridge-playing habit, his odd hours and that he took telephone numbers from other women.
Mike Tomkies, the Fleet Street journalist who abandoned the life of a celebrity reporter to live alone in the wilderness, lived with her for a while in Canada and they talked of marriage but she was prohibited from marrying by a contract for The Champions (1968 to 69). He said that she was the most stunningly beautiful creature he had ever seen.
In 1980, Alexandra married Patrick Garland a director, writer and actor, at Chichester Cathedral, who became a long serving director of the Chichester Festival Theatre. Bastedo wrote a memoir, Beware Dobermanns, Donkeys and Ducks, as well as several books on caring for cats and dogs. Her younger brother, Lindsay, died following a long struggle with cancer. Her husband died on 19 April 2013.
Bastedo was a vegetarian and is the founder of Alexandra Bastedo Champions (ABC) Animal Sanctuary. In an interview on the BBC television series Where Are They Now? Bastedo provided a glimpse into her private life. She used to be the president of her local RSPCA branch but gave up her position in 2008, to dedicate more time to her fast-growing animal sanctuary at her home in West Chiltington, West Sussex. A journalist who interviewed her husband in 2010, described their domestic surroundings,
[W]e sit in his Sussex garden looking towards a small lake with a jetty and a battered rowing boat – a perfect pastoral scene which could be a stage set. He lives with his wife, the actress Alexandra Bastedo, who remains startlingly beautiful, a couple of Dobermans, some territorial cats, and a menagerie of horses, donkeys, pigs and goats – Bastedo runs an animal sanctuary. Garland's domain is largely inside the house where he closes doors to keep animals out of rooms lined with 12,000 books.
She was also a patron to a number of animal welfare organisations including Compassion in World Farming, Wildlife Aid Foundation, National Animal Welfare Trust, Greyhounds in Need and Naturewatch.
She died from cancer on 12 January 2014 aged 67 in hospital in Worthing, England.13 Frightened Girls (aka The Candy Web) (1963) – Alex – England
The Liquidator (1965) – Radio Operator (uncredited)
Doctor in Clover (1966) – Nurse at Party (uncredited)
That Riviera Touch (1966) – Girl at Roulette Table
Casino Royale (1967) – Meg
Wedding Night (1970) – Gloria – Girl Friend
My Lover, My Son (1970) – Cicely Clarkson
This, That and the Other (1970) – Angie
The Kashmiri Run (1970)
The Blood Spattered Bride (1972) – Mircalla Karstein
I Hate My Body (1974) – Leda Schmidt
The Ghoul (1975) – Angela
El Clan de los Nazarenos (1975) – Arima
Tu dios y mi infierno (1976) – Liselotte
Find the Lady (1976) – Victoria
The Man Inside (1976, TV movie) – Joan Lytton
La Gioconda está triste (1977)
El Mirón (1977) – Elena – wife
Cabo de vara (1978)
Stigma (1980) – Anna
A Choice of Two (1981)
Draw! (1984, TV movie) – Bess, Harry's Girlfriend in Bell City / member of acting troupe
La veritat oculta (1987) – Agnes / Chiromancer
Batman Begins (2005) – Gotham Society Dame
The Count of Monte Cristo (TV series, 1964) – Renée de Saint-Méran
The Scales of Justice (episode The Haunted Man 1966) – Laura
The Wednesday Play (1966) (TV) – The Girl
The Saint (episode "The Counterfeit Countess", 1967) – Mireille / Joan Vendel
The Champions (TV series, 1968–69) – Sharron Macready
Randall and Hopkirk (Deceased) (episode "Whoever Heard of a Ghost Dying?", 1969) – Carol Latimer
Codename (1970) (TV series) – Diana Dalzell
From a Bird's Eye View (episode "Sicillian Affair", 1970) – Lisa Vespucci
The Aphrodite Inheritance (miniseries, 1979) – Helene
Legend of the Champions (TV, 1983) – Sharron Macready
Absolutely Fabulous (episode "Fat", 1992) – Penny Caspar-Moorse
EastEnders (2008–2009) – Cynthia (final television appearance)