Polo Heater Blows Cold

[harpersimon]

Hello

I have a 1998 Polo 1.4 - and the heater only blows cold. Started a few days ago. Was stuck in traffic, car started getting a little hot so I put the heater flat out to try and cool it.

got home, noted that coolant was alittle low, topped up all fine. ONly the heater blows cold!? Opertaing temp is normal, no issues, got a new Thermostat about 4 weeks ago.. any ideas? Can I bleed air from the heater somewhere? could it be the heater knackered?

Thanks anyone!