The title of the British movie....?

Recently I've seen a very interesting British comedy: it's about a
woman who is caught on a train with a trunk filled with pieces of
bodies of her husband and his lover, whom she killed because of an
obvious reason.) She is sent to a madhouse, of course, but later on
she manages to escape and found her doughter, whom she is tryng "to
help" to save her marriage.
The problem is I can't remember the title of the movie!!!) Could
anyone help me out here?

P.S. Maybe you know any other British comedies (movies) worth of
watching?