So, I did the spark plugs (all 16 of them!) last weekend. They didn't look too bad at all really for 70k miles. Changed them outside the service schedule (I think its 100k) and put in some OEM equivalent NGK ILFR6A. Runs a little smoother (possibly placebo!) but it reports a slight increase in mpg for a journey I am used to doing so I call it a win.
Unfortunately, I did notice the inevitable valve cover and breather cover oil leaks starting on both banks of cylinders (common issue on the M113 and M112 engines). Starting to make its way down into the spark plug recesses and makes everything around the ignition coil packs really untidy

So I cleaned it all up temporarily and ordered the full set of replacement gaskets, breather hoses and sealant- which is next weekend's task!
I also, swapped out the recently changed Pagid front pads for genuine Mercedes ones - the Pagid ones squealed horribly at low speeds and low braking levels - it was just not acceptable. Seems to be a common thing with these (unsure whether it's something specific with these calipers and pads but the OEM ones are happily squeal free!)