I have just picked up the following from an article in the Newsweek section of this week's Auto Express.
Basically it says, that under new EU proposals, any kind of modification could mean the car fails the MOT. If the proposal gets the green light then "components of the vehicle must comply with characteristics at the time of first registration" effectively outlawing any deviation from the factory specification. This would make the rest of the EU the same as the situation in Germany. Any car fitted or modified in any way that is not TUV (the German car testing authority) approved would mean the car would fail an MOT. This would include wheels, bodykits, headlights and even towbars.