Since it is a loan (as opposed to Hire Purchase), then the vehicle is yours and yours alone. You cannot hand the vehicle back as the finance company have nothing to do with it- they just gave you some money which you chose to spend on a car.
If you stop paying, then you will be in arrears and then in default. The loan company will take you to court and have a county court judgement issued and then may ask for an "attachment of earnings" order which means that your employers would pay deduct money from your wage to pay the the finance company.
Try selling your car privately and hopefully pay off your loan with the amount that you receive.
(just as a quick thing, make sure you double check your finance document to ensure it was a Loan and not a HP agreement - it will be printed on the top).