Getting off topic here, but that makes three of us who checked the "West Australian" for the alleged letters to the editor -- Peter B, you and me.
I hired the microfilms for July and August 1969 for a small interloan fee, studied them, took copies of most relevant articles and letters and did typescripts of them. Any members are welcome to copies.
Interestingly, the microfilm boxes had an address on them: The British Library, Newspaper Library, Colindale Avenue, London, NW9 5HE.
So I don't see any reason why Bennett and Percy could not have checked the "West Australian" for themselves and found exactly the same as we did.
IIRC Percy claimed that copies of the newspaper must have been changed to exclude the letters. Un-bloody-believable!!