The timescales are implausible. The Series begins a couple of years before WW1, and Emma seems to be about 20. However, the present day is set in the 70s. This would make Emma well over 80 in the present day and her eldest child in her 60s - none of them look old enough.
The transatlantic liner Queen Elizabeth on which Paul McGill says he is booked to go to the USA in 1939 was not completed until 1940 and did not enter commercial service until after WW2, about 1946. He may have meant the Queen Mary.