That's a little worrying as apparently VW fitted the Matrix. I bought the car from someone who worked at VW (not in the garage itself though).
So fixes?
Sound like someone has replaced the Matrix and not put it properly back together again...
The middle vent section is a pig to refit properly...
My air only blows to feet and/or windscreen. Is that the gear gog? If so what's the fix?
With the fan on full, give the heat and direction sliders a good working over. Poor air speed could be that the seals around the door flaps in the fresh air box are shot - telltale sign is small bits of plastic foam coming out of the air vents.
If the direction slider doesn't work then the gear gog at the bottom of the fresh air box had slipped loose - fiddly job.