Can some one tell if if the problem I have is with the heater fan or resistor, when I turn the heater on the fan tries to move but doesn't now I've had the fan out and it seems to spin ok when I do it manually but when u connect it and try it it rocks back and fourth and doesn't spin the whole way round

 

Motor brushes failed most likely. Easiest option would be just to get a new fan unit from a breakers.

 

I agree with Richie. The fact that it's trying to turn suggest the motor is faulty to me!
You could use a multi-meter to check the voltage to it.