From what I recall the UK cars are fitted with interior sensors, they were mentioned way back when I was new here. The UK cars also have safety triangles to be put up behind the car in a breakdown or accident situation and a medical kit. I believe EU rules later dictated two triangles plus a fluorescent vest. These are good ideas I think, I have a triangle and the medical kit, both have a Mercedes part number on them. There are various triangle and medical kit part numbers. I have the ones with what I believe to be the the UK Mercedes part numbers plus the same set of items with other part numbers.

I asked once what cutouts were required in the rear trunk trim, sizes and location etc to attach the Velcro strip to, but I received unusable sizes that did not give some sizes so I gave up. They are in the trunk now under the mat. They never came with North American cars, the thought was that it was legally better to let someone die rather than get sued if you aided them and they died anyway.

These days people react very fast when they see an accident or someone in trouble, they get out their phone and record the scene and in some cases rob the victim, good Samaritans are harder to find these days. 🙄