AXA. I got some horrendous quotes when I was looking but as I was insuring 2 cars at the same time AXA managed to sort me out with a good deal. Essentially they matched my NCB on both vehicles and then ave me 15% off the most expensive policy as a Multi-Car discount.
Their individual quotes were very competitive though so worth a look, however my car is standard so if you're looking for modified car insurance Im sure there will be better available.