Originally Posted by xenon
A new (additional) driver increases their perceived risk irrespective of her driving record and consequently they can make a charge. You might have more of a complaint if you were exchanging a high-risk driver for a lower risk driver but they're entitled to levy a charge for adding an additional one. Whether that charge is fair or reasonable is open to debate but this is not at a level at which the ombudsman will have any interest.
I'd say that this depends. If the OP is suggesting that no additional milleage per annum is incurred by adding a lower risk driver, then you could argue the lower risk driver is now doing the milleage the a higher risk driver is currently doing. I have heard cases where people have lowered there premium by adding lower risk drivers to there policy (never happened to me though) however this seems to have had to opposite effect.