I have a MY10 TDV8, if I leave the heating set at auto and say 22 or 24 on the dials both front seats experience colder air in the footwell, or at least no warm air. On long trips this can be quite uncomfortable. The only way around it seems to be to turn of a/c, turn on the the lower vents only and turn up the temperature.

Has anybosy else noticed this, or is there a fault on the system?

Try:

Set the temperature to max.
Set the vents to feet only.
Set the temperature to a more normal 22-24 whatever
Press Auto.

Sometimes I get no air from the front dash vents I then select vents only then press auto and the system seems to distribute the air normally again. It sounds very similar to your issue (even though a completely different system)

That being said, it sounds more like a blend motor has failed for you - the system has probably already diagnosed a fault but there is no warning message or light etc for the HEVAC system. Might be worth asking the dealer to check for hevac codes.

Dan 

Brillient, thanks I will try that.