I wouldn't touch flux again if they paid me. I had no issues with them sorting out a none fault claim 9 years or so ago but a couple of years ago they disputed NCB and I had various issues over data protection (they sent me several other peoples paperwork, bank details etc). Their customer couldn't care less team were shocking.
With sports cars and anything else a bit specialist I wouldn't bother with confused.com etc they don't search the specialists and I've always found them to be quite expensive.
I have two cars, an 06 impreza wrx and a classic mini. The impreza has been insured with greenlight and I couldn't fault them, I have been through none fault and fault claims (2007 was a bad year) both times I got everything sorted and the my car repaired by who I wanted. The only others that have got anywhere near them are A plan. The impreza is standard apart from coilovers and I pay about £500, 9 yrs NCB, business mileage and 2 accidents in the last 5 years. Greenlight actually prefer modified cars as they see it as if you've gone to the effort to sink more money into the car and make it more desirable then you're probably going to look after it a bit more than a run of the mill dirt box.
The mini is insured via Footman James, I haven't been through a claim with them but I get breakdown cover, unlimited mileage, declared mods for £100. They weren't interested in NCB but did give me a discount for being a member of an online mini forum as they
classify it as being in a club.
I've heard good things about Keith Michaels too but they've never been competitive enough for me.
www.greenlightinsurance.co.uk/
www.aplan.co.uk/
www.keithmichaels.co.uk/