Importing and Exporting a vehicle from the UK

http://www.direct.gov.uk/en/Motoring/BuyingAndSellingAVehicle/ImportingAndExportingAVehicle/index.htm
Registering an imported vehicle

The procedures and documentation required to register an imported vehicle
Temporarily importing a vehicle

Temporary use of a vehicle in the United Kingdom
The Single Vehicle Approval scheme (SVA)

Details of the SVA scheme operated by the Vehicle and Operators Services Agency