I had the same.
First, turn the temperature up, stick all the airflow down into the cabin and crank the fan up (I'd advise doing this with the engine on, or your battery will drain very quickly) - check there's air coming out of the vent on teh side of the centre console by the clutch pedal.
If there is little or no airflow, you need to take off that panel, and look see if there's a small unit with white arms on it that move around when you alter the direction of the airflow, eg press for windscreen, face vents etc. Mine had seized up, freed itself with just a little nudge.
If the airflow is poor coming out of the foot vents, try taking out the pollen filter, and leave it out. I was getting cold air blasting from the ides of the filter housing, made my feet cold and f-ed up the climate control. Even with a brand new filter in.
Once you have warm(ish) air coming into the footwell, my advice is to set the temp to about 22C. Press Auto, then press the cooler button - you don't need the compressor running this time of year! That should then keep the car warm. If you find your hands getting cold, press the windscreen button, and warm air should start coming from the top half of the car too.
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