Escaping claim payment

My car was insured with Iwyze. It was written off & the person who drove it took it without my permission whilst I was asleep. I lodged a claim and submitted all documentation & info. Required. After several months of playing hide & seek, the assessor never notified me of the progress of the claim until I heard from the salvage Co. That I must come & collect my car as Iwyze rejected my claim. After several phone calls to Iwyze, they sent me from pillar to post. I had to seek advice from a lawyer. It's now almost 2 years & still no positive response from Iwyze. The only response from them was that the driver was under influence of alcohol. 2ndly they say they confirmed to the lawyer in writing that they assumed that "I gave permission" to the driver who is actually died in the accident. Although I stated the opposite. How can Iwyze work on assumptions by themselves whereas all information is recorded by themselves when I submitted the claim, telephonically. Please help.