That hurt!! The other day I had exactly the same in the snow with a opel astra but with just some minor body damage. Understeer really sucks... you feel so stupid when the car is going straight and you can't do anything! well, you can brake a little to put some weight on the front wheels to help them get a grip or also accelerate to "neutralize" the understeer. I haven't tried this last one myself (just heard it in top gear) cos I haven't driven a rwd car yet...