So, I've started!
Almost instantly I've found something out, which I've not seen anywhere mentioned online.
This is the image commonly thrown around when ICM deletes are discussed:
Whilst it's technically correct if you are just bridging across the ICM using a plug in delete, if using it to do a decent job and wire in a full replacement loom, it's very missleading!
When it says Coil 1-4 at the top, what it should actually say is Firing order.
The top row of pins, from pin 1 to 4, actually don't go to coils 1-4 in order at all.
Pin 1 to Cyl 1
Pin 2 to Cyl 3
Pin 3 to Cyl 4
Pin 4 to Cyl 2
So, 1 3 4 2, which just happens to be the firing order of a 1.8T.
So, if bridging across with a plug in you don't care where they go or in what order, but if splicing in a new loom it makes a huge difference.
It turns out the ECU doesn't fire in the engines firing order. It simply fires A B C D for example, then the hardware (wiring in this case) is wired in the correct order to determine the firing order. so ECU outputs 1 2 3 4, are actually wired to the coils 1 3 4 2 respectively.
God knows what would have happened if I'd just run the pins to the coils as per number order.
Given this 'interesting' discovering, I think I'm going to make all the other connections permanent, and just twist and tape these by hand for an initial first start just to be sure it starts up OK before I solder them all.
Have I mentioned before how much I HATE wiring?
I think I'm on top of it, but this stuff makes my brain hurt!