Brian is playing the game so well. He has studied BB extensively. He could even remember the week numbers that Alex and Adele got evicted. He was also telling them things that they had forgot themselves. Who the hell knows this type of stuff off the top of their head?
That combined with some of the other things he has said in the past, he's not as stupid as he appears. Same goes for Carole. They are the train spotting anoraks of the BB world and know the score when it comes to BB.