Except, you know, voice actors can do different voices. The guy who voices Astarion literally did a Russian accent for a recent Resident Evil game. The use of all British accents in the game was a conscious choice, not due to mechanical limitations.
I never talked of "limitations", but since their native British accent while speaking English is as much a good fit as it gets for a medieval setting, there was not particular reason to go for anything different, either.
