My own. I was born and raised in the United States and I use the Northwestern accent I've always had. It has been discussed in several threads that pirates from the colonies of the period would probably have more of a colonial accent anyway, so I avoid a forced accent.
William Brand was born in England, but sent to the colonies at too early of an age to be greatly influenced by accents of those cold, damp climbs. He's also lived in too many places to be grounded to one country by his mode of speech or any accents.
When in doubt, I always say 'play you'.