Penhaligon had roles in films such as Say Hello to Yesterday (1970), Private Road (1971), Under Milk Wood (1972) as Mae Rose Cottage, No Sex Please, We're British (1973), The Land That Time Forgot (1975), House of Mortal Sin (1976), Nasty Habits (1977), Paul Verhoeven's Soldier of Orange (1977) as a British military officer, The Uncanny (1977), Leopard in the Snow (1978), Patrick (1978), The Masks of Death (1984) and Top Dog (2014). She also played the role of the sole survivor of LANSA FLIGHT 508, Juliane Koepcke in the film Miracles Still Happen (1974), directed by Giuseppe Maria Scotese.

Her TV credits include Count Dracula (1977) with Louis Jourdan, Upstairs Downstairs, Tales of the Unexpected, Bergerac, Remington Steele, Wycliffe, Doctor Who, The Taming of the Shrew by the BBC Shakespeare series, Heart of the Country and A Kind of Loving. In A Fine Romance, she played Helen Barker. She has been in three episodes of Doctors and three episodes of Casualty. She also played Jean Hope in UK soap Emmerdale, for a year.

In the West End she appeared in a 1987 production of Three Sisters at the Albery Theatre. In 1982, she played a leading part in The Real Thing at the Strand Theatre, Aldwich (now called the Novello). She appeared in The Maintenance Man at the Comedy Theatre in 1987, and played "Curley’s Wife" in a 1984 production of Of Mice and Men at the now defunct Mermaid Theatre. She has toured the UK extensively, appearing in productions of The Constant Wife (Richmond Theatre, 2004), Mrs. Warren's Profession (Richmond Theatre, 2009), Death Trap (Theatre Royal, Norwich, 2002), Agatha Christie's Verdict (Floral Pavilion Theatre, 2011), Dangerous Obsession with Simon Ward (Theatre Royal, Bath, 1989), and Lord Arthur Saville's Crime by Oscar Wilde (Richmond Theatre, 2005).

Her novel For the Love of Angel, published in 2008 by Truran Books, is set in Cornwall in the 1880s.