It would not be unreasonable to expect privacy during your vacation time .. And this 'arrangement' should have been discussed with you before permission was granted to these friends. Your boyfriend has 'spoken' for you, instead of asking you opinion about it .. And although that is quite typical amongst couples who know each other well .. In this case, he was wrong in thinking you'd be ok with it.
This is something you are going to have to either sacrifice a night to accomodate your boyfriend's decision, but tell him that you are NOT ok with it, and he SHOULD speak to you about this sort of thing before he makes promises that involve your 'space' so that THIS kind of thing never happens again, AND that two nights are out of the question .. Or .. Speak up and air your differences with him, and ask that he tell his friend this just may not be such a good idea, and that the friend should get his own room .. Which may ulitmately result in his embarassment in front of his friend .. AND make you out to look like the 'bad guy'. In any event .. This situation needs to be discussed with your boyfriend, so this kind of thing doesn't happen again .. ever.
