Just done it recently with my Motorbike. Had to purchase a new car after accident in January so needed to get rid of bike.
Contacted Moto Novo with a Voluntary Termination template off Google sent recorded. They responded a week later. They organised Crystal Collections to come collect bike.
Make sure you have all service history and go round and take pictures of your vehicle.
They will bill you for any missing service records, scratches and V5 etc.
About two weeks after collection They contacted to say account balance zero and account closed.
You have to have paid 50% before you can do a Voluntary Termination.