I like many have seen many rusty SLK's and many MB's generally with very bad rust those pictures do not suprise me in the least.
Just think, the 210 front spring cups can rust off, quite a few threads on this.
Looking through the paperwork it doesn't look like it has.
As far as the Nissan Navara are concerned they are well known for the rusty chassis that was made in Spain. While Nissan don't admit there is a safety concern have a look on the facebook page of Nissan Navara snapped chassis page - assuming you have a facebook account. They are literally snapping in half.
Does anyone know who is in charge of Mercedes UK customer services? Even better if there is an email for them as well.