Will be checking stuff over the weekend, car not being used currently. Will also check heater matrix, give it a flush perhaps?.
Interestingly it was at BMW specialist in May last year and they reported the issue but never got asked to look into it. Invoice says bled system twice but still blowing lukewarm.
Flaps were mentioned but I thought it would be hot in some areas and not others because of a failing one or is there a MAIN flap for all?