i have a gap at the bottom on the 2 door velvet rubbers of each about 10 cm, i thought that was to evacuate air out of the compartment when driving with closed doors and fan working.
No, the gap at the bottom of each door surround seal is really just because the seal was often slightly too short! I have door body seal surrounds that meet and form a complete 'circle' and they keep out drafts and water!
The exit vent for cabin air is behind the internal 'B' pillar trim and it goes through a slatted vent in the chassis 'B' pillar, and then is pulled out by the air flow past the external 'B' pillar body trim, at the back, via the gap between that trim and the glass. If you ever take off the internal or exterior trims, you will see the slatted vents.
You will also note, if your internal trim is a light colour as with my grey trim, that those internal 'B' pillar trims get very dirty over time owing to the airflow (which carries dirt) getting around and behind them, to vent out of those slats. The air exit has to be in a low pressure area which you get just behind the external 'B' pillar trims. (not at the bottom of the doors!)
As for the cabin air intake, as with all very aerodynamic cars, the air wants to simply flow up and over the car, so you must keep the fan on at least speed one to promote air flow through the cabin. And yes the intake hole is tiny - it almost looks like a water drain point, but even with the fan shield replaced by a grill to give a larger intake, you still need the fan on, as it is not the air entry size that is restrictive, but the aerodynamics that stop air flowing through the heating system naturally without the fan drawing the air in.
Roy