I used an independent meet and greet parking service at Heathrow Airport recently. When they returned my car the leather part of the driver's seat was ripped. I told the guy who dropped off the car and he took a photo of the damage and sent a complaint to the firm's customer services department. The independent parking firm has got back to me and said it accepts no liability for the damage as they subcontracted the work. They also say they did not damage the car and accept no liability for any damage to the inside of the car. What should I do?