Yep would seem its the idler arm...just need to find one now?.
Now I'm thinking, i bought a steering damper recently from the following link:

eBay - The UK's Online Marketplace

In the list of merc models that the damper was compatible with it lists numerous different models....does that mean the idler arm would also be compatible across these models?, for instance I have found an idler arm for a c-class 1.8 (this model was in the list of compatible models on the damper link) link here:

MERCEDES BENZ C-CLASS IDLER ARM 1.8 93-00 OE QUALITY | eBay

Does this mean that this idler arm would fit an slk 320/crossfire?
Sounds confusing & hope I've explained things as best as possible