The one I flew, (which on reflection was A321 I think), had no air blowing onto my feet, the heat came from under the floor somehow.
I also seem to remember there were PBs on the overhead panel to select them on/off.
Oh, here we go - I was nearly right. From Airbus A321 FCOM:
The foot warmer system@ has a heating panel attached to each pedal. The temperature of the panels is about 20 °C (68 °F).
Applicable to: ALLThe Foot Warmer ON/OFF control switch@ is located on the main instrument panel, on the captain's and first officer's side.