Yes it is a fault. PSA are getting away with murder. Every time someone (who has parted with a vast amount of money to them) complains they either say they know nothing about it (see my posts on ECG) or its normal for this vehicle. No its not. When you come to trade in your present new car, and all 2008's are reasonably new, you will see how the amount your car will fetch is affected by the "unknown" faults that you are now suffering from. The trade and other customers will shy away from these cars.The diff noise is due to faulty diff gearalignment caused by bearing faults. They should put this right for you.