The likely answer is Yes - when you say finance, are we talking HP, PCP or Personal Loan.
Presuming PCP or HP, each finance company will have their own terms and conditions - call them and find out the processes and facts and figures.
If you're looking to sell the car then use the 'cash' to pay off afterwards, the buyer may not be happy as they are effectively buying a car from you that doesn't belong to you! What would they do if you took their money and then didn't pay off the HP...
Of course....you've also got to find a buyer!