The only reason that adding the other half to mine is costing me more is because she's only got a provisional licence... Should go down once she's passed her test.

Its funny the way that some insurers reduce the premium if you add certain types of drivers (even if they may never actually drive the car). My brother has just bought a Citroen C2 GT and is looking to get insurance on that, he ran a quote through Elephant for just himself and it came to £600+, I told him to run a quote through with our mum as a named driver and it reduced it to £430! WTF is that all about?