So I am suffering a TATL Y trip on Sunday, and MMB says the WT cabin starts at row 21 (centre 3) and 22 (window rows). However neither sueatguru nor BA's own seat maps agree with this config... I think it's a 4-class 777. Any clues? Am I already looking at equipment swap that was not in the originally loaded fares/flights?

Not that I am that bothered but curious really... I have found BA to be quite good at getting the seat selection maps right.