Housing issue

So this Thursday I am going to be moving into a new student house down in Brighton.This will be my 4th year there and I know the rental market is HORRENDOUS. however I wasn't quite prepared for this. I viewed a 7 bed house and the rooms were all a nice big size with sinks in the room, a desk, bed, wardrobe, and chest of drawers. Except for one. One of the rooms was very small and only had a sink and a bed in it. I viewed quite a few more properties and then my halls lease was up so I moved back home.

I rang up the letting agent the next day and put down a holding deposit and they informed me only room 3 was available. I asked the woman if it was a double room and she said yes so I went ahead with the agreement and paid my deposit and first month rent. Drumroll pls, I have the tiny room. There's no space for a desk, chair, or chest or drawers. Just a doubled bed and wardrobe crammed into the space with a sink in a 75sqft box. Is there anything legal requirements for the size of rooms or any steps I can take to get my rent lowered/ make myself feel not quite crap.