Very interesting M.E. Coincidentally I recently changed my car and moved from up from a 2002 1250cc. 3 dr. Hatchback to a 2010 1400 5dr. hatchback. I had previously queried what the rise in premium would be from my Insurance Company (not A.A) before I bought it and was told it would be "minimal". So imagine my reaction when a demand for £270.00, a rise of £101.00, fell onto the doormat!
I duly phoned the company and asked to speak to their Loyalty department (as I also do every year with my Buildings/Contents which is with the same company), and they immediately reduced it to £180.00, an increase of £11.00 from last year, which I thought was very reasonable considering the change in value and engine size/specification etc. of the new car to the old vehicle.
Like M.E., I have also had reductions in premiums year-on-year so it does show that you should never accept the first quote in (unless it is cheaper, of course!) and a call to the "Loyalty Dept. can work wonders.