If you plan to take care of the whole import process yourself there are a number of steps you have to take. You need to inform HMRC that you are importing a car by completing form C384. You'll also need insurance for the car in France while driving it to the port, but this can be problematic unless you have a registered address in France.

The age of the Citroen means it does not need vehicle approval, but it will still need modifications to the headlights, speedometer and rear fog light if one is not fitted. Once you have completed this, you can apply to the DVLA to register the vehicle in the UK.

Alternatively there are several import companies that will take care of all this for you, which may be more expensive but will require a lot less effort on your part.