It's from the same director and the same writer who did "The Last King of Scotland". It's about an OCD American girl sent off by her father to live with her aunt and cousins in England. She falls in love with her oldest cousin... and then a nuclear bomb goes off.
It's like a teen romance version of "The Road". I have never seen a movie which makes England look as beautiful as this movie does. I really, really like this movie.
Bonus: It's on Netflix! Edit: No longer on Netflix! Damnit!