Felicia 1.3: no heat/airflow, even.

Hi. I have a 1.3 felicia. It's a great little car. One problem. When I put on heater it makes all the right noises but hardly any airflow through vents ( they are open ). None at sll from the ones nesr the doors. I checked the housing and the twin fans are spinning as they should. Slso, the temp rarely registers on it unless I tick over in traffic. Then it gies straight back down. I know I need a stat but any ideas about why no airflow through vents. Incidentally I had the car idling while I delved into the heater fan box and it went up to 85 or so and it was hot in the car but still didn't feel like much airflow.
Bit stumped.
Thanks