Well, we did the ice pack thing...
It did seem to improve it slightly, but that could have been a coincidence.
He is keen to buy a new coil.
Since we fixed the A/C it has put a larger thermal load on the cooling, and I feel it has got worse.
If you stp the car for 10 mins, it gets better until the engine is reading 90deg and then it starts again.

__________________
2009 Mercedes ML320 Bluetec