Does it matter? its a film about a character who's actual existence is yet to be conclusively proven, not a historical documentary.
If you wanted to be 100% accurate the English being spoken at the time of Robin Hood was so different to the English we speak now you would need subtitles.
That is brilliant news. It's a huge topic of conversation at my work, and I know it'll please the others I work with. Can't wait to get back now after my lunch break and tell them!! Yay!!