Continuity mistake: Juliet is on the bed with little girl Kit. The child has a ribbon is her hair then looks up at Juliet and it becomes a slide. Next cut it is a ribbon, then a slide. Then the girl sleeps on Juliet with just a ribbon visible. (01:19:00 - 01:20:00)
Factual error: The plane used in the film to take Juliet back to London towards the end of the film is a replica of a Dakota C-47. She is painted with black and white "invasion stripes" on both the upper and lower surfaces of the wings - approved in May these were only widely put into use for D-Day in June 1944. After one month the upper surface stripes were ordered removed, and by the end of 1944 they were ordered completely removed. By 1946 when the film is set they would have been long gone from any serving aircraft still flying.
