Synopsis: "London is a big city, and for those new to it, it can seem quite scary. But Tomoko, who arrives from Japan to learn English, accidentally discovers a mysterious, secret city underground, inhabited by friendly little aliens and beautiful blossom. After she found it everything changes...".
The director Gaëlle Denis is French, but she actually moved to London in 2000, to study at the RCA (Royal College of Art). The movie has been produced by Passion Pictures.
The music is by Jocelyn Mienniel, while the closing theme is Peach, Plum, Pear by Joanna Newsom.
More info: http://www.imdb.com/name/nm1538811/
I am not Gaëlle Denis, but here is the way to contact her (thanks Google):
33-34 Rathbone Place
London W1T 1JN
T: +44 20 7323 9933
F: +44 20 7323 9030