Ford Fiesta 1.25 Zetec Heating not working?

Can anyone please tell me where the heating valve is, and how to replace it? I have no heat at all, and the kids and I are freezing! Both pipes are hot, and the temperature gauge is showing as normal, so I assume it is the heating valve?

Ive replaced the resister as the blower was only working on speed 4, but just need heat now.