ADAC are a good one to go for.
IF a car is old and has a low book value. They will NOT recover.
However if you argue with them. They often ask for the car to be taken to the nearest Subaru dealership and whoever looks at the car there talks to ADAC head office and if he knows what he is looking at they will recover. If he does not and does not put your case forward. You are stuck.
Your car can also be confiscated by the German police. This eventuality is highly unlikely as you lot only go to Germany a few times. Most police are not interested and would not know how to go about it any way as you are on UK plates. A very few policemen can stop and confiscate - it will be on noise and lack of cats in the exhaust. This seems to be more of an issue in the south of Germany than arround the ring area.
I am sure that you will not hit any issues as as a rule Germany is one of the best countries to drive in Europe with a UK plated car
