In your induction day did you get to look around the boarding house at all? I boarded part time at my school, although I was in the female house (it was a co-ed school), and pretty much everyone, unless they specifically asked to share with someone from year 9 and above, got their own room. I was only there for three nights a week and I got a single room even though I was more than happy to share with others. Of course this all depends on how much space there is in the house, it's lay out, and how many people are staying there, but it wouldn't be unusual at my old school at all. The sixth form house was almost entirely single rooms as far as I know.
Just expect some quite bizarre routine rules, for example not being allowed to brush your teeth before breakfast but having to leave your tooth brush in a box so that you could do it afterwards in a room with only three sinks and then collect it that evening. Actually breakfast was even more bizarre, who has fish fingers for breakfast?!
