ScubaVideo
Contributor
For a Brit like yourself, "octopodes" is preferred, followed by "octopuses," and then "octopi," which is only acceptable because pedants lost the battle to a relentless sea of ignorance. "Octopi" is the plural you would choose if you thought the "-us" was the Latin noun ending that takes "-i" in plural, as in "radius," "stimulus," and "nucleus," but it is actually derived from the Greek "pous," meaning "foot."
"Octopodes" sounds too stuffy for me, and I don't want to have to explain it every time I use it, so I go with "octopuses," and smile condescendingly whenever somebody uses "octopi."
Umm, taken care of in post #5 - see the video.