How does rubbish like this ever get made?

Why oh why do great actors such as Colin Firth ever get involved in low budget, poorly scripted unrealistically shot nonsense such as this?

Very poor. I laughed exactly twice: Once in the bedroom scene where Colin Firth's character tries to smother his snorin wife with a pillow and once at Jack Dee's curmudgeounous reaction to trying to get to sleep in the hotel where the couple next door are making mad, passionate and excessively loud love!