Thanks for the speedy response silverteam!
Incidentally, I used OE parts from the local stealership.
I couldn't actually see or feel any wear at all, but was advised to change the bushes and ball joints by my local MB specialist independent at the annual service in Oct. They know I'm keen to keep the car in mint condition and at my request they point out problems at an early stage, so I tend to replace things before they fail. As I usually do the work myself and buy the bits from MB, they have no financial interest to generate work and I trust them (a friend uses them too). The car had already just passed it's MOT (annual extensive safety check) without advisories (suggested work) and the bushes and ball joints seemed ok to me, but I did the replacement anyway.
I'll run the car for a bit (I'm about to do 1000 miles to Scotland and back) and see if there's any sign of tyre wear.
John