VT is a statutory right built into every finance agreement and is often suggested by dealerships when they want to sell a new car. It has no affect on your credit rating as you are considered to have fully met the terms of your agreement. In my experience, the Finance houses generally take care of VTs by auctioning the car, as well as billing you for any pro-rata excess mileage and any rectification to paint, body work, wheels, interior or documentation.
If you think about it, vitually every finance agreement has negative equity built in. You pay linear payments across the agreement but depreciation is strongest in the 1st and 2nd years. This is why you need good gap insurance in case the car is stolen or written off and you are left owing a lot more than your standard insurance pays out. Dealerships' GAP insurance is about twice the price as buying direct from the insurer...