In the light of the above thread I thought I'd post my recent experience...
Sold it. Yes, my Jeep Wrangler went to its happy new home leaving me with a pile of cash to spend elsewhere. Supposedly it was a group 14 insurance. 2 months before, it cost me just over £320 (GBP) to insure for the year.
Within days I'd bought myself a Mitsubishi Carisma 1.9 diesel. Group 10 insurance. I called my insurance co (yes car insurance) who wanted an additional £180 to insure it for the remainder of the policy. (10 months) That would have made the premium paid around £500 for the year.
Whilst on the phone to the insurance co. I explained that their need for the additional premium was silly, and they need to find me a better deal. By changing policy they came up with a deal costing £370 for 12 months. I duly coughed up.
Returning home, I visited money_____ etc (You know, the internet place on the TV ads) who confirmed that the best deal was with my new insurers, but I should have paid £70 less than the telephone price. (Should have paid £300)
Moral: Shop around. The internet search engines are worth the time to enter all your details...