If I legally change my car registration number, can bailiffs still remove it?

Yes

The bailiff may take control of goods only of they belong to the debtor.^[1]

When bailiffs recover an unpaid traffic contravention debt, or a court fine involving a traffic offence, the warrant of control will show the registration number of the contravention or offending vehicle.

When bailiffs attend the debtor, they drive round the neighbourhood and look for the vehicle, and if they find it, they will clamp it before calling on the debtor.

If you change the registration number, to a cherished plate, then it makes it harder for bailiffs to identify the car belonging to the debtor.

^{[1] Paragraph 10 of Schedule 12 of the Tribunals, Courts and Enforcement Act 2007}