It's a while since I saw a production, Keiva, so forgive my hazy memories, but I thought the ongoing joke was quite the other way around: they are all noblemen living a life as pirates, yet speaking in u/c accents, aren't they? [but confused!]

I am sure you are right, whichever, that the accent is to do with class or its pretentions - "Are you orffen heuh?" can still be heard on the terraces at Glyndebourne