Well, by coincidence, my mobile phone wasnt charging properly earlier this week, so after trying a new lead and it not making any difference I tried scraping the accumulated fluff out of the bottom of the cigarette lighter scoket with a needle file..... with the ignition on.. D'oh! - big spark and blown fuse
So I was out this morning to find that 15A fuse Number 1 in the engine compartment fusebox had blown. I know mine's a W210 but Id be surprised if there was much difference in a relatively simple component. - And there was a list of which fuse does what inside the fuse box.
In case you're wondering . turns out my phones knackered..
Its fuse 1 on the early 210s but fuse 2 on the later ones, and the 211 is nothing like it with far more in the way of electrics.