Ngaire - you might want to include on your cancellation policy that it's the Ring of Fire cruise as well as the world cruise on the Mariner that have these cancellation penalties in effect.
On a separate note, I found a typo on the B&K website.
http://www.bkrssc.com/I_Payment_Cancellation_Terms.htm The first two sentences:
"Cancellation fees will not be waived by the cruise line. If you select a different cruise date and you are in the cancellation fee periode cruise line. "
:D
Masaki