Clare,
Don't spend extra money on a 2 bed unless you want it for yourselves without the CP'er!! Both of my kids have been a CP and believe me, after they get roommates and friends in the program they DON'T want to stay with family when they visit!! I started out like you, booking 2 rooms etc. They are having so much fun there that it is almost hard to track them down at all! Although, they do seem to turn up for (free) dinner....