It is five years, yes. As to whether Ford are obliged to put it right, technically yes. However, whether they will do so depends to some degree on the attitude of your Ford dealer. If, as appears to be the case, you have any trouble getting them to do the work, ring Ford customer services first, and if their response isn't satisfactory then write a polite but strongly worded letter to the head of Ford UK. I'm sure someone here will have the address.