Welcome to the forum Rob you'll find the members on here are a friendly and helpful bunch 🙂
Sorry to hear of this situation, they should be giving you an extra service as the error is there's. My advice would be to speak to Audi customer services, the motoring ombudsman, citizens advice or trading standards. At the end of the day you've paid for a goods (the service components) and services (the actual work) but not received them.