What makes you so sure the heating pads are defective, rather than the controls, the switches, the fuses, or the connecting plugs? Have you checked any of them?
It would be a shame to throw good money after bad by renewing pads that may be perfectly good, but if you happy to pay for the job to be done there are plenty of people in your area willing to do it. Hint: they all have Audi in their company names.