Thanks guys

Had to make a quick decision before reading all of your advice, and mechanic worried me into the piston work as well, I'm afraid.

BTW the car (now affectionately known as *****face) was originally on synthetic by the look of it, but I changed to mineral at post-purchase service, as this is original merc spec. Shortly afterwards trouble began.
Coincidence?
I hope so, or I'm looking like a muppet. :)

Alex
190E 2.0 auto 155k
190E 2.6 auto 110k