Peter,
It is interesting that the response to the reading of the Laurence Binyon's poem 'For The Fallen' is, in Australia, "Lest we forget"; elsewhere in the world it is "We will remember them". Do you have any idea why Australians use "Lest we forget"? I would be interested to find out.
It seems to be a phrase very much associated with the ANZAC remembrance, Legacy was formed by returned soldiers to care for the wives and children of those who did not return. In fact I believed it to be the Legacy motto. If I recall there was a bronze torch mounted on a plaque on the wall with the words "Lest we forget"
Now that you have jolted my memory I believe the response "We will remember them" is often used too.