Damn JJ,
You must have gold lined pockets...... £5k is a hell of a lot of money to spend on a car, in the space of 1 year aswell.......
im not planning on keeping mine forever maybe till next summer max. I cant use this car practically to be honest. we have a c class aswell, so that compensates i suppose to a degree....
I have asked a few people and its not related to the cats.. but if i was you i would get all servicing done by MB but then get additional work done by a indie specialist. but each to thier own i suppose.

Raj