The heater in my roomster only blows cold air

Hi i have only had my roomster two weeks and really love the car but the heater is now only blowing cold air, all blower setting are working but the temp control is now hard to move.

I surpose its a trip to the main dealer who i hate, my dealer can't do warranty work anymore , so has anybody got any ideas please ,it should be done under warranty, and its the first failure on any of my skoda's since 2005.

Thanks

Edited 19 May, 201214 yr by Mick 50