At the end of the film when Helen and James are on the bridge, her hair is wet when James is explaining his situation. Then when she is crossing the street to use the phone, its still raining but Helen's hair is completely dry.
When James and Helen are sitting in the diner, they are drinking pink milkshakes. As the shots cut back and forth the shakes disappear and reappear. Also in the next scene James talks about drinking chocolate shakes, even though they were pink, not brown.
At one point Helen chastises her house mate for asking her "more questions than Jeopardy". Jeopardy is an American quiz show that has only been briefly aired on British television. Even though it is well known in the UK, it isn't sufficiently part of popular culture that two British women would use this show as an analogy.