Hi,
It wasn't long before I'd nose around here.
Gino, as Alessandro said the Olympic's sitting rooms were smaller than that of the Titanic. Yes Cameron must have fudged. The sitting room is way too big for what the real one was like (not to mention it was the wrong style too) also has furniture that was never in the room.
The promenade in the movie is way too big too also not to mention various inaccuracies in the decoration.
As for the B1 cabin it really is quite simple, however it had taken me months to realize the answer is obvious. Just simply looking at the picture the ceiling is MUCH higher than an A, B or C deck cabin (although the Boat and A deck cabins had 6" higher ceilings than B or C deck). The room is evidently a D deck cabin, where the ceilings were 10'6" (as opposed to 9' or 9'6").
This is (as I have said) a picture of a D deck cabin. It's from the Olympic after it's 1913 refit. For those who have the Olympic May 1913 or June 1914 plans (or even later) the cabin can only be Olympic's D23 or D29.
This explains why the window is at the fore end of the room as this is not usually the case, and the window is usually in the middle of the room. In this case the inner cabin was removed to accommodate a bathroom and the outer cabins were enlarged, so the porthole that was once down the corridor from the inner cabin is now the fore window of the new, larger cabin.
I hope that's helpful and solves the problem for all.
Daniel.