Did you you know it is illegal to display your national flag on your registration/license plate?
in 2001 the UK up held and passed the EU law to ban any national recognition on your registration plate, it carries a fine of £60.00 with no appeal allowed under EU law, also includes the Scottish Saltire. Welsh dragon, St Georges cross etc etc.
Regarding the guy with the mini, according to the Police, if you have a union jack on your car roof its classed as racism, as it could be offensive to other people that aren't British. They told him that he has seven days to remove the graphics or could be given an asbo or worse.