As you can see in that last picture of the inside of the 800ES/B, there's not a lot of free space, and certainly not enough to cram all of the Gaggiuino control components inside. I wasn't entirely comfortable just putting the control box on the outside, as it includes mains-voltage components. So instead I modified the standard Gaggiuino control box so that it could be mounted inside an off-the-shelf project box. Actually, I just used the clear lid of the project box, but the electronics are encased in a tough and fully insulated case.

Here's the enclosure that I used: https://www.jaycar.com.au/sealed-polycarbonate-enclosure-with-mounting-flange-171-w-x-121-d-x-80-h-mm/p/HB6223. This comes from a local Australian supplier, so I'm not sure how available it will be to everyone else. I would actually recommend editing the OpenSCAD file to match whatever enclosure you can find