Aon have been around for years. They run a classic car rally every year too, so at least they seem like they are interested in cars!
Be careful if you are using one of their specialist car policies though. Their 'Roadster' policy (underwritten by Royal & Sun Alliance) with limited mileage is designed for second cars and you don't get ANY no claims bonus with it. When I wrote off a Supra about 3 years ago, I had quite a task to get a decent settlement from them too. In the end I made enough of a pest of myself that when I offered to accept their first offer (which they had refused to increase in over a month of arguing) on the condition I could keep any salvage I wanted, they finally agreed, probably just to get rid of me.
Worked out ok for me in the end, but I didn't renew my policy with them. I'm with Norwich Union Direct now.