bailiff is demanding money about a vehicle you never owned.

Bailiff companies trace people with unpaid traffic contravention debts by phishing,^[1] including putting money demands in letterboxes of homes the bailiff thinks the debtor might be living to see if it gets a reaction.

There is no need to contact the bailiff company. It will come to nothing.

You might have been named as a driver when the keeper returned a Notice to Owner.^[2]

If you are named on the warrant of control, you can apply to suspend the warrant,^[3][4] on the grounds you never owned or driven the vehicle.

^{[1] See Bailiffs leaving a phishing letter or document
[2] Section 172 of the Road Traffic Act 1988
[3] Civil Procedure Rule 75.9
[4] See: Appeal parking ticket after bailiffs}