Insurance pricing is odd.. I recently looked around on the comparison sites for a cheaper policy for the wife. When I put her in on her own it came back as £580. When I added myself as a named driver it dropped to £280. Neither of us have made a claim or had an accident in 30 years (the only previous claim was for a stolen radio).
Its with direct line now as it was cheaper than the comparison sites.
I also noticed that it costs more to insure my corsa than it does the wife's Astra even though the corsa has a smaller engine, lower top speed, etc. They appear to think they are more likely to get stolen or something.