Originally Posted by JEEMO

Is it the inside of the rear tyres that are wearing mate? I had a MK5 Zetec-S that had been accident damaged and the beam was bent slightly this caused my rear tyres to wear on the insides very quickly. If the wear is quite even I would check the bushes as if they are badly worn the rear beam can move side to side whilst the car is in motion and cause the tyres to wear. If you can get the car in the air try and shake the beam and see if there is a lot of movement ad the rear bushes are quite a common failure and are an easy DIY replacement. Polybushes for the rear beam are around £30 delivered from ebay and stiffen the beam.

Hope this is of some help to you mate.