on my 6n2 tdi i have just had some powerfelx bushes fitted on my front wishbones and i have had them on for about 2month and the rear bush on the passenger side of the car had completly collapsed i thought it was a fault with the bush as all the rest of them are ok it has been replaced but now the same bush is on its way out again what could this be???

Sounds like there's increased fatigue on it - possibly by steering alignment,brake bias,anti roll bar fouling the chassis,something loose there causing the bush to take impacts,worn damper,something like that.