My Mrs has been through simular except it wasn't her car it was her house
Police victim support gave her £50 to replace all her and her daughters possesions and her ex husband got away with it scott Free as there wasn't enough evidence to suggest that he was involved and the police didn't have concrete evidence that he had set it alight when the Mrs and Daughter were meant to be in the house... (Luckily they had decided not to go back home that night and to leave it til the next day but her ex Husband knew that she was due to be at home that night to start packing ready for moving as the courts had told him to stay away from that road until the Mrs had packed and moved..wasn't even his house!!)
Hope you get a bit of luck sorting out your car...There's some real physco ex's out there and the police do absolutely nothing
Did you report her setting alight to your Audi?