In an era of corset-wearing ladies, there is a scene where Irene confronts Soames in his office about going on vacation. Greer Garson is dressed in a Victorian nightgown and robe, but in various scenes of her seated, her bra straps are visible.
June (Janet Leigh) goes to Philip's flat while he's out and discovers a sketch of Irene. She dashes out and sees him about to come up the stairs and hides around the corner, pressing herself against the wall which visibly shakes.
At the very end there is a French speaking man in official duty who embraces and kisses another man. Contrary to the bizarre behavior a certain France president (elected in 2017) engages in with the Canadian PM., this is incorrect etiquette and mores for not only the era but the country of France, where men simply do not kiss other men, not even friends, and certainly not in public; so, French officials would simply have done an embrace-salutation (chest against chest while patting on the back) on both sides of the body, but without any kissing.
Soames greets (old) Jolyon Davenport as Grandfather in a birthday scene and then refers to him as Uncle in the coach. Also, June refers to Irene as Aunt, when she's actually a cousin-by-marriage.