As you have a Y reg - i think you will have a 3 speed fan - when they fail it is a question of replacing the bushes - search on e bay they are inexpensive -£20.00ish.
If you have a 2 speed fan then it is usually failure of the resistor - go to the front of the car -look RHS through the grill - can you see a resistor - silver in colour 4-5 cm's long - if so you have a 2 speed fan you will see a resistor - if so the resistor needs replacing with a gold coloured upgrade - £15.