Thank you, Anna, for referencing Lanie's message! But, I'm still in the dark as to when Candace Glendenning died. (Much as I've only just heard--and not been able to verify--Michael Jayston's death.)
I am aware of the situation involving Lynne Frederick's last years. I found a highly acerbic biography, The Life and Death of Peter Sellers, which presents some very sad--and often frightening--details re: not only Peter Sellers, but also of Lynne, his final wife. She married and divorced twice after Sellers died--one of her husbands being David Frost--and died on April 27, 1994, having been a drug addict and alcoholic, as well as severely overweight.
Quite a contrast to the real-life Tatiana, as well as the schoolgirl-like voiceover Frederick provides for the featurette included with the Nicholas and Alexandra DVD.