I'm giving this 5 stars for the story idea, for Michael Caine, and of course, for Jane Horrocks. Horrocks as LV is so vulnerable, and her performance is so affecting, that I was absolutely smitten.
I thought about giving it 4 stars because I thought the love story with Ewan McGregor's character needed more screen time. (Their scene at LV's window is straight out of classic Hollywood.) However, the performances more than made up for that minor flaw.
The psychological angle to this movie is interesting. LV is stuck in the past, stuck in her room, and stuck in childhood. She talks like a child, she's in pajamas a lot of the time, she's got a child-like haircut and a little bed... There's the scene where her mom barges into her room while she's sitting on the floor playing records, and she looks up at her like a deer in headlights. In that scene you could mistake her for 13 rather than 34. Even though LV's behavior can be pretty creepy, she never seems as delusional as her mother or Michael Caine's character, which is why it's such a joy to cheer for her.
I love this movie so much it would be great to see an American remake, perhaps with Zooey Deschanel or Maya Rudolph as LV. I'm a Zooey fan, but I thought of Maya in the scene where LV goes crazy on Michael Caine's character. I think I've heard Maya do similar voices.