Thats the only reason I can think off to explain using an English lead and an American.
Now I have to say I adore Alec Baldwin, perfectly cast in The Shadow and The Hunt for Red October but like all Americans he cannot do an Irish accent, and Ms Cooke while equally talented is also hamstrung though not so badly, her accent at least touches the four provinces albeit it does them all at least once in every 3 words, where Baldwins lands somewhere in Iceland trying to escape Boston.
This will likely be lost on an international audience but for this Paddy it makes the film unwatchable.
Now I have to say I adore Alec Baldwin, perfectly cast in The Shadow and The Hunt for Red October but like all Americans he cannot do an Irish accent, and Ms Cooke while equally talented is also hamstrung though not so badly, her accent at least touches the four provinces albeit it does them all at least once in every 3 words, where Baldwins lands somewhere in Iceland trying to escape Boston.
This will likely be lost on an international audience but for this Paddy it makes the film unwatchable.