This is where I'm going to start putting my photographs of UK registered cars. Please feel free to contribute.
EU legislation
Under EU law, a private vehicle may be temporarily imported and used on French roads for up to six months in any 12 months. The vehicle must be re-registered in France if it is owned and used by a resident of France.It is against the law for the resident of an EU country, while living in that country, to drive any vehicle registered in another EU country. So a person who is a resident of France may only drive a French-registered car while they are in France (with the exception of cross-border workers).
An EU-registered vehicle must satisfy the legal road worthiness requirements of its country of registration to be legal to drive elsewhere in the EU.