Left home for a meal last evening and returned to find a bit of a mess in the kitchen
What caught my attention were bits of ceramic insulation about the place

Thought is
pressure stat stopped cycling
overdrove element
boiler pressure relief valve opened, see pic for displaced insulation

Machine is 24/7
When found at failure
Power indicator was glowing
Pump engaged and water flowed out of the group
No steam / hot water

Not sure where to begin the process of proper diagnosis

Your diagnosis sounds accurate, but incomplete. If the Pstat jammed and the safety valve opened, the boiler will subsequently refill and cool somewhat, so the vale closes. Then the cycle will repeat until the tank empties. At this point the heater either burns out or a thermal protection device shuts the heat down.

This means the first step is to check the heater -- reset any safety devices, replace any thermal links and check the continuity of the heater. Once that is done, the boiler should heat up. If the boiler overheats, you will need to try adjusting or exercising* the pstat. If that doesn't work, it should be replaced.

* sometimes the membrane freezes and it can be unfrozen by exercising it, i.e. pushing it back and forth using a toothpick from either the steam end or the switch end.

Thanks

I have
(with power disconnected and water supply off)
Cleaned up the insulation mess
Opened the Gicar box to look at the boards, no visible burning
Measured 7.3 across the element
Reset a fuse in line with the p-stat, blue arrow points to it in pic
Restarted machine and all is functional

The thermal fuse tripped, and no harm done. You will need to keep an eye out for the pstat, especially if it is a Mater or Ceme, since these are prone to sticking, and once they start, they keep doing it at increasingly frequent intervals.

Beautiful

Replacing Pressure Stat
My local parts guy, Bill, has a Sarai and the machine has space for it under the hood

Now for some new insulation

In my admittedly limited experience, SSRs either work all the time or they don't work at all; they don't fail intermittently. If the unit ran after Pietro's repair, this would seem to clear the SSR as the suspect.

Ah. then its worth checking if the contacts are carbonized. Arcing can freeze them together.

You can see the relay, Siemens 5TT3 984 (no longer produced), to the right in the above photo
It moves freely, I will try to peer inside
http://support.automation.siemens.com/WW/llisapi.dll/csfetch/6006460/505078910DS01.pdf?func=cslib.csFetch&nodeid=6006461