I'm amused but not very surprised to see that others have previously compared this to "Amélie."
Bella Brown (Jessica Brown Findlay) is an obsessive compulsive young woman who works at a library and aspires to be a children's writer. Her grumpy next door neighbour Alfie (Tom Wilkinson) files a complaint with her superintendent about her garden, which is a mess. In the first of many bizarre twists, Alfie's house keeper Vernon (Andrew Scott) quits his employment with Alfie and comes to work for Bella. Vernon's encyclopedic knowledge of city law earns her a reprieve on the garden, but she has to fix it in a month. In the mean time, she gets to know Vernon, Alfie, and an eccentric young inventor (Jeremy Irvine) who frequents the library.
For those expecting a realistic movie, no: this is a fantasy, a surrealist fable similar to "Amélie." It's not as good as that movie was, but if you accept some particularly odd behaviours (and an inaccurate portrayal of OCD), it can be a very enjoyable movie.