I'm going to answer this one myself.
After waiting a few weeks, the supplier delivered my new PCB... In a small white box...
Then came the challenge. Opening the coffee machine. I searched for a service manual, no dice. So I emailed Delonghi to see if I could get one. No dice. Apparently they consider it a health and safety issue if I fix it myself. But did offer me their price list for repairs. £175 + VAT for a broken PCB (Which is about £55 if you buy one online from delonghi spares). So taking careful note of their concerns, I exercised my rights and continued to fix the damn things myself.
A thorough investigation started. After quite some time, and a bit of head scratching, I found a total of 3 self tapping screws underneath and another 4 behind the water container. All useless. Don't bother if you're trying this at home.
Some time later, after the top cover for the bean reservoir annoyed me enough, I noticed that the hinges had small lever on them... And it came off... Then after investigating all the little plastic clips etc and the way the panels fitted it because apparent that the rear of the machine needed to come off first. And the only way it could come off was upwards... A bit more poking & prodding (And a few swear words) and there's a small plastic panel that sits at the rear of the bean reservoir and provides the recess for the hinges themselves. And that comes off to reveal 2x self tapping screws holding on the rear panel.
Removing those, and the rear panel slips easily upwards. Showing...
Two more self tappers (You can see one in the photo above, the other being removed already), and the side panel around the water reservoir also comes off. Revealing at the top of the machine the PCB!
Now wires... Lots of wires... Take plenty of photos and note where all the cables run to. Some of them look extremely similar. The PCB itself is held in by 4 small self-tapping screws. And some of the space for pulling wiring lugs is pretty close. Remove all the cables and the PCB, plug in the shortest cables and then seat the PCB in place and place the rest of the connectors where they go.
Note carefully the really close spacing of the terminal connectors at the rear of the board
I was initially a bit worried about all those really close bare bits of metal. But a quick look at the rear of the PCB and testing with the multi-meter reveals that all 4 of those connectors are actually the same connection. A big earth pad perhaps.
A quick re-assembly and lo! We have Power! But in Italian... Not being an italian expert was a bit of an issue, but eventually I got the machine back into English and ran a quick test. It all works! Great.
So what went wrong?
Taking a careful look at the PCB reveals no evidence of shorts or melted transistors, the big power transistor with the heat-sink is pristine. Caps all look good... A closer look was required... Then I noticed one of the resistors... Just a small bit of white residue on the sides. But it looked strange. And appears to have a hairline crack across it. Using my multi-meter it only has 1.8 Ohms resistance. Which doesn't match the replacement... Or the values it should be from the colour codes. So a dodgy resistor kills my coffee machine.