Hi wee Hugh
Have you checked for her death under her maiden surname?
There was a death notice in The Times on 20 April 1965:
NICHOLSON on April 19, 1965, at Little Orchard, Limpsfield, Surrey, peacefully after a long illness, ALICE widow of JOHN HERBERT NICHOLSON and dear mother of Margaret Mathews and Sheila Nicholson. Funeral at St Peter's Limpsfield on Wednesday at 3:15pm. ..
Unfortunately John Herbert's death notice just says beloved husband of Alice
Dazey