welcome to the mad house.
do the heater control knobs feel ok,???
it might be the linkage has broken,you can see it if you take out the glove box and look at the control lever while you move the controls.(on the side of the heater box)
has it got water in it.??????????
BTW there is a self test for the heating ..its something like hold down the AUTO button and turn on the ignition and wait for the fault codes to be displayed..i cant remember WRINX will tell you he has it .i think
Check out your hot water valve on the end of the matrix, you will need to get the left hand side dash out which is a s**t face, of a job. A recent leaking tap caused me to delve into the dark depths of my dash, when I set the temperature all the motors worked fine, even the valve seemed to move correctly. However when I took the valve off the spindle had broken inside so there was no control. Mine failed open so i was hot all the time, I guess yours failed shut.