***SPOILERS***
If the movie was set in 1931, and world war 1 ended in 1918, and world war 2 began in 1939, then Ed would have had to age 13 years, MINIMUM, between the end of the series and the movie. From the previews I've seen, he doesn't look one day older or one inch taller. :/
And I DISTINCTLY recall somebody named Churchill wanting to meet with Edward's father near the end of the series, and since I don't believe Churchill served in World War 1, or would have had much rank, I'm forced to assume either World War II or that they made up an entirely new war.
Besides, I'm pretty sure the Battle of Britain in which the massive bombing runs occurred was in World War II. I'm forced to conclude, in short, that they mixed the two wars to make the series more entertaining.
***END SPOILERS***
Remember, just because it LOOKS like our world, doesn't MAKE it our world.