BA planned that they only needed 4 midhaul config A321s when they converted 3 of them to standard European configs. However they are at a point where they are due checks and as such EDF has been in Madrid for a month. With only 3 in service they can't operate the full schedule. Pretty disgraceful really. With that seating they are interchangable with a 319 pax number wise and all should have been kept in Midhaul config to prevent this sort of nonsense. BA really do seem on a mission to drive their regular customers to the competition.
They have no brake fans either so when regularly on the Aberdeen runs I imagine the crew prey for a bit of wind whilst at the gate!