I also have a radio reception problem 2003 C class 200 Kompressor, as long as I am in my local area, the reception is fine, drive out of area very hit and miss.
Was thinking of adding a roof ariel, any suggestions.

 

Ariel antenna will permanently solve reception problem. My model is different but I had the same reception problem as yours. I strongly recommend Hirschmann aerial antenna. My choice was manual because there is no maintenance. Go for it.

 

Thanks for that, not being very technically minded I assume the antenna is within the rear screen, and having access to another car making the same journeys without reception problems but using a traditional external antenna just seemed like a no brainer.