Mark sends a note to Juliet explaining that he managed to bully his way through the slow line at customs. He asks to see Juliet and says he needs to talk to her. Juliet suggests they eat a sausage at her flat, but he wants to go out. Juliet makes him say "please" before he agrees.
Again, Mark's tone demonstrates a lack of concern for anyone but himself and a desire to control and bully Juliet. Making Mark say "please" first indicates that Juliet isn't giving in without a fight.