So we've been told the DR is upstairs this year - and it makes sense, because if you take the 3D Tour of the house - you'll actually see that there is two chairs upstairs near the entrance.
Usually housemates get told off for even going upstairs if it isn't an eviction.
Which, makes me think - that there may be a 'tunnel' like in BB5-BB7, that separates the initial first staircase from the rest of the house.
Reason being - look at those two doors, they just look too plain and simple to be a door to exit the Big Brother house, can you really picture the sliding doors on the exterior to go with that? They won't. There has to be some sort of room beyond the entrance, that separates it - otherwise they wouldn't have two seats upstairs, because housemates aren't allowed within that close of contact with the main door.
Also, the Diary Room door - I'm convinced is one of these and I'm leading towards the red door. It's just strange that there's no 'lock switch' above it.