I have a 126p and noticed the flap below the thermostat was open about 1" when the car was cold.
I fitted a new thermostat and it's exactly the same - consequently the hot air flow through the heater is poor.
Is this flap supposed to close completely when cold?
My previous 500 & 126 cars had fantastic heaters within 200 yards from cold - my latest car is poor even at high revs when hot.