My STC-1000 is installed. Woohoo!
Here's some notes:
I sited the stc-1000 / stc1000 25mm above the existing control centre. This was mainly to clear the existing wiring, so I could get my hands in there.
There's plenty of room here. I gave the corners of the hole a light tap with the punch before drilling, it keeps the bit in place.
I drilled out the corners with a 1.5mm (2mm?) bit, then cut between the holes with a cheap-****(TM) angle grinder (1mm cutting disk).
Oh, you need a 72mm by 30mm hole, but best decide on this size for yourself.
The thing holding the power cable in has those 3-flap screws FAARK! I replaced these with some phillips. Getting these feckers out was the hardest part of the job. And I even had a bit for it. You have to be so careful working around those coolant pipes.
I pushed my screwdriver from inside the "compressor hump" right through. I'm not sure it's 100% perpendicular (it's close), but it comes out on the wall of the hump. The metal interior of the freezer is basically only a medium foil. Pushing my screwdriver from the inside of the hump made a dent in the foil on the inside the freezer. I simply pushed (a bit more firmly) on this dent from the inside, found the hole and managed pentration. Maybe I thumped the back of the screwdriver with my hand, I can't remember.
So ... it seems I missed the coolant system. I have attached photos of about where I put my hole.
I just guessed this position, but I did take a good look to make an educated guess at what direction the pipes seemed to be going first.
I undid the power cable and pulled another 15cm through for the wiring. This was enough, but it was still pretty tight.
Once I had the heater and sensor wires pulled through my hole I siliconed it up on both sides. The wires together filled the hole I made, so I couldn't see the point of extra insulation, there was nowhere to put it.