gbtransp:
orys:
Well, German internal law can’t rule over the international agreement when the foreign registered vehicle is in question. If the car is legal in UK, it is legal in Germany.
Correct!!! Contruction and Use
I am glad that we agree that my statement above is correct altough I dont’ really get why you added “contriction and use” to it. 
orys:
There was a similar case few years ago about German giving out tickets to foreign cars for not having a first aid kit on board. When Poland started to fine German cars for not having fire extinguishers they found that the tickets were actually unlawful and paid it back to the Polish drivers
Correct !!! Construction and Use
Not really correct. Polish goverment tried to negotiate with Germans, but they were claiming that this interpretation is valid. Only when Poland started to use this interpretation to fine German registered cars, their changed their mind. At the meeting in Świnoujście in March 2008 the Polish and German police forces agreed to the proper interpretation, that is the one which takes Vienna Convention in consideration. After that meeting Polish drivers had their fines for not having first aid kit refunded, and this few Germans who were fined had their fines for not having a fire extinguisher refunded.
Fire extinguisher in Poland is a thing which every car has to be fitted with and it’s checked on MOT. I was controled with my British registered car or van on many occasions in countries which require fire extinguishers and I had never any problem with not having one. They cannot fine you for that, as it is tied to the car.
But for example it’s not mandatory for driver to carry documents with him in UK, but it is mandatory in Poland (Germany/whatever). Therefore you can be fined for not having your logbook with you, because it’s not technical requirement to have car fitted with document, but it’s a driver’s duty to carry paperwork with him.
orys:
German like this things, years and years ago I remember another case -they were fining cars with non-removable towing bar, which were legal (and AFAIK still are) in most Eastern European countries (and also it seems in UK as well). Again, someone refused to take ticket, took the case to the court and win.
Correct !!! Construction and Use
I agree that we have the same opinion on above: if the towing bar is legal in country of registration, Germans cannot fine anyone for having one fitted when driving in Germany 
All foreign vehs must stop at a “stop sign”
Correct !!! Highway code
This one is not about vehicles but drivers. It’s drivers who have to stop at “stop sign”. It’s driver who drives the car, therefore highway code apllies to him, not to his car. It has nothing to do with technical requirements in one’s car’s country of registration. Therefore altough you are off course right, the analogy here is fraud.
All foreign vehs must drive on the right
Correct !!! Highway code
Last time I checked HIghway code, it was written that everyone should drive on the left
Off course you are right if you think about Pravidla silniÄnÃho provozu, Das Straßenverkehrsgesetz or Kodeks drogowy. But the same note as above apply in that case 
All foreign vehs must giveway to the right(unless otherwise stated)
Correct !!! Highway code
Again the same.
All Foreign vehs must be fitted with winter tyres
Correct !!! Because it is law in the German highway code and not the Construction and Use
Not correct. Because Vienna Convention says “The vehicle must meet all technical requirements to be legal for road use in the country of registration. Any conflicting technical requirements (e.g. right-hand-drive or left-hand-drive) in the signatory country where the vehicle is being driven do not apply.”
And since Vienna Convention is an international treaty, signed and ratified by Germany, it stands above local law (in this case this ones you call “Construction and use”).
Thereofore Germans cannot fine you for not having winter tires, altough they have full right to fine you for blocking the road, dangerous driving or whatever they want, as long, as it applies to DRIVING, not to the car specification.
I rest my case 