A contributing factor could be that a slightly higher percentage of international students go to off campus because unlike on campus halls, you don't have to move all of your stuff out over christmas/easter and obviously moving your **** back to the other side of the world is a hell of a lot more annoying than getting your parents to whack it in the car and move it to Bristol or wherever. But as someone who lives here now, whilst there is a decent mix, the strong majority of students are british.