I can understand why the key would normally not be covered by the warranty because it would be subject to wear and tear over its life, but in this case when the car is basically brand new I think you do have a case for the key to be replaced free of charge. In my view, based on what you have told us, Subaru should replace it as a gesture of goodwill. I am surprised and very disappointed that the Dept. of Fair Trading has dropped it simply because Subaru has not responded to their requests. That undermines the credibility of the department. I would seek legal advice on the merit of your claim before taking Subaru to court.