Greenlight have been by FAR the cheapest I have found, 27 yrs old, 8 years NCB, no points garaged in a decent postcode as a second car, all mods declared (400BHP+ loads of expensive bits) with agreed value of £16k comes out to £797 fully comp with protected NCB's and a lowish excess..

Boncaster = useless, never ring back, hard to get hold of, expensive, don't like mods
Adrian flux were ok, but poor modification protection IMHO.

Greenlight have always been very helpful, actually answer the phone, have superb knowlegde of cars and mods etc, ring you back when they say they will and generally offer top top service, hence why I will 99.9% re-insure with them again this year

And I think I have rung virtually EVERY insurance provider in the UK, and most of them were not even in the ball park, and the others were unhelpful or uncompetative..