Engine Oil De-Gunk

Morning,
Not on a Landy, as they never keep oil in the engine long enough to become gunk, but on my Merc (V6 3.2)

Back story:
Last week I had the Coolant Level warning pop up on the display so I filled it up with the correct stuff and all was OK.
On my way from the Lunnen & SE LZ Meet last Wednesday, I was sat in traffic by Chiswick Roundabout for about 30 mins and when I got to Twickenham all was fine. When I left 'Nam, I noticed the car had dropped all its coolant - obvious from the wet patch under the thing and over the road...

Popped the bonnet, filled the expansion tank back up and then popped the oil filler cap, knowing pretty much what I expected to see...

The cream gunk stain of death...

Sure enough, there it was.

I was overcome with distress and sadness, plus I could feel a pain in my wallet coming on. I drove home and parked her up, then spent a fortune renting a car (BMW 120 - too small but goes like a scalded cat) as I had a golf tour last weekend.

When I got back to Lunnen on Tuesday I made some calls and the local indie Merc place in Harrow said they had never heard of a V6 of that year ever doing a head gasket. They said look again at the oil filler cap - no sign of the cream of death, but the thing looks really gunked up.

So, long story short, what is the best engine flush to use to de-gunk the engine? It's likely breather tube issues and is going into the place in Harrow on Wednesday for some investigations.
I got to use my new Snap On Verus Diagnostic tool and there are no faults showing up, so it's likely something physical...

Any ideas chaps?

Cheers

All sorts of concoctions but this is pretty good.
https://www.forteuk.co.uk/product-detail/39/Bio-Degreaser-Cooling-System-Flush

We're all fairly familiar with flushing the radiator and cooling system but most people wouldn't ever consider using a flushing oil on the inside of the engine. It's not a cheap option, it usually requires filling the engine to half ful and running it for a few minutes or so to work it around the oilways then draining out and filling with the proper engine oil.
There are numerous manufacturers on the market so the link below is just an example.

http://www.halfords.com/motoring/engine-oils-fluids/engine-oil/power-maxed-engine-flush-treatment-325ml
http://blog.greenflag.com/2015/are-engine-flush-and-fuel-additives-worth-the-money/

Ah, the memories of the Redex cloud drifting over the neigbours washing line when I was young, as I revved my old Opel Manta....