I'm glad that the series uses British accent instead of American. Feels somewhat turned off if movies/series depicting ancient and medieval fantasy period uses American accent.

Movies regarding modern times that does not happen in America also usually uses British accent, for example Enemy At The Gates. Not just because the actors are English but I guess that's the way it is.

Futuristic movies mainly uses American accent and only characters for different species usually uses different accent.

For example John Boyega speaks American instead of his native British accent since Finn/Stormtrooper in British accent sounded out of place.

There were movies/tv series that uses American though it shows ancient rime period and they turn me off everytime. Like Xena Warrior Princess etc.