There are two valves on the inner nearside wing that control the flow of hot water through the heater matrix check that they are working if they are ok then you need to look to see if the blend flap motors are working there are three but you need to look at the ones for left and right - my guess is it is the heater valves on the inner wing.

Thanks to you all. It was the inner wing control Valves. They were both stuck to some degree.