Her first credit below was filmed 50 years ago.
There’s no guarantee of completeless here. She was in a lot of British projects in the 1970s and 80s, and she was already an adult then. There was a bit of nudity in those shows, and I know very little about that world. If you know of more scenes, please let the rest of us know.
1976 – Bill Brand
1981 – Excalibur (She’s still MY Guenevere)
1985 – King David
1986 – The Monocled Mutineer
1988 – The Man Who Lived at the Ritz
1996 – Strangers
Cherie is in her 70s now, so don’t expect any more nudity, but she’s still working. She’s up to 114 IMDb credits, including one this year.

Agree with you as best Guenevere. But she could’ve been nakeder in that movie…
Fun fact – the actress playing Igrayne (and getting banged by Uther in full armor) is Katrine Boorman, the daughter of director John Boorman. Must’ve been a fun scene to shoot…