I VT'd 3 years into a 4 year contract, although when trading in against a car of the same make from the same dealer as i purchased the first. One phone call to the finance company and a they sent through some forms to sign. I didn't sign the forms as the wording would have made me explicitly liable for damage etc. Instead i wrote them a letter telling them i wanted to VT as was my right and that the car was ready for collection at a time of their choosing and was in reasonable condition. This was important as legally you are only obliged to return the vehicle in reasonable condition and provided you do so they cannot charge you for anything they deem outside of this definition. I think it was moneysavingexpert that described in detail how to do this and i used this as a template
http://legalbeagles.info/forums/show...tter-Templates
The finance company then sent a chap to inspect the car and another to collect it (although he also checked the car). Both noted various chips etc and asked me to sign a form confirming the 'damage' which i declined to do and the car was taken away. A few days later i received a letter from the finance company saying no money was owed.
I think that essentially trading up with the same dealer, manufacturer and finance company helped. It may be that they decide to press any supposed claims for damage etc if you buy outright, although in reality other than send threatening letters there's not much they can do as no company has yet been prepared to test the reasonable condition definition in court in case they lose and set a precedent.