Fiesta - No heat from heater

[The Guv]

Hi, I've just bought an 05 Fiesta Zetec but on the trip back to Canberra we found that the one thing we didn't check - the heater - didn't work. Considering we've been below 0 regularly for the past month it was a surprisingly warm drive back in 2 shirts, a jumper, jacket, explorer socks and beanie.

So I've been doing a fair bit of research and checked the physical cables from the switch to the valve (I think it's the valve), checked for leaking coolant, checked fuses and found nothing. I know it isn't the blower resistor because the fan works at any speed too.

So I need to go and buy a Haynes manual as I think it's been narrowed down to the heater control valve or the core being clogged. If the pipes I found were the right ones, they were the both warm, one more than the other so I think that rules out air in the system. I haven't been able to hear the blend door actuator do anything so that's an option too.

So that's where I'm up to, but if anyone has any experience with this it would be great to hear as I'm pretty new to fixing stuff on more modern cars.

Thanks