have you got air in the system? try burping it... start car, take to a steep hill, turn off, have radiator at highest point, take radiator cap off (make sure it's not hot etc), turn it back on, turn heater on full blat on hot, start topping up the radiator till it stops bringing bubbles up, cap her off and see how the heater is then
also the heater unit... theres something you can remove, like a little leg, i think it's clipped into the side, they go faulty occasionally so unclip it and see if the heater works then...
sorry that last one may be a bit of fun to figure out lol.. best i could explain at the mo.. maybe someone else can explain that one better
