Ford Fiesta 51 Plate heater blowing cold air

[gilbmw]

I have a ford Fiesta Flight on a 51 plate. The heater is only blowing cold air. I have checked the coolant level and this is on Max and also flushed out the heater matrix. As the pipes were cold after the heater control value and hot before it, I replaced the heater control valve. but the heater is still blowing cold air, and the pipes are the same cold on one side hot on the other. Has anyone come across this before. I don't want to replace the heater control panel unless I need to, is there a way of checking this is faulty before replacing this (I have a multi meter), or could it be something else?

Thanks in advance