Chesdroog

Having recently been told by my local garage during a routine MOT that my back box has corroded and needs replacing I thought I would have a ring around local garages and find the best price. To my amazement none of the garages stocked them and only one garage said they could source a replacement at a cost of £180 but would not come with the tip (which they could not source). Surely I cannot be the only A1 driver who has needed a replacement?? What are other peoples experience of this? Is going direct to Audi the only answer??