I have a Vauxhall Corsa 1.3 CDTI EcoFlex and initially when I bought it the heater resistor we thought was broken as the blower fans would only work on dial 4, we replaced it and it worked for about a week and it only works on 4 again, thats my first problem!
Secondly, this may be related but my heating takes an awfully long time to heat up and if the engine is running but the car is idle it blows cold air after about 10-15 minutes of solid driving it finally slowly heats up?