Insurance premiums are indeed a mystery. The best quote I had for my Civic at the end of last year came to about £380 from Churchill. Recently I have been looking around for my next car and getting insurance quotes online, so out of curiosity I stuck the Civic details back in just to see what came up. £230 through Admiral!
I can only ever remember getting a reduction in premium once or twice in the last 15 years, despite an almost perfect claim history (one claim against 3rd party ~9 years ago), and my premiums have always been very high for my age and car (most likely due to location). So how come my premium has suddenly dropped by 40%? Not complaining of course...just curious.
One annoying thing is that I started a policy with Norwich Union when I got my MR2 and had 5 years NC from my previous policy (also with NU). When I sold the car about 4 years later and got my proof of NC, it still said 5 years. This would be fine...but going from the online forms, some insurers appear to accept more than 5 years NC.