I saw thw film as part of 2 couples snd we agreed that it is a good film, worth seeing. We too had reservations about Hugh Bonneville, not his acting but his look, but we had none about Gillian Anderson, Michael Gambon and the rest of the cast.
Personally, I could have done with less of the love story but I do understand that it ran parallel with the politics and helps paint the picture. Hopefully, it will also bring more people in to see an important and tragic part of history. We 4 cinema-goers contributed half the audience (and possibly brought the average age down) although it was a 5.30 pm showing.
I have no reason to doubt the accuracy of the history but I shall be interested to check it out. I think the film quotes Churchill's 'History is written by the victors'. I am not sure who the victors are in this film but the Director gives an even-handed view of the main protagonists and makes her own engaging contribution to the history.