So dimming works, remote control works and temperature measurement all works. For some reason Lux measurement is not working, I think I may have fried that sensor by accident.
Cabling is still somewhat of a mess, but I was thinking of sorting that out when the lamp is moved to it's final place.
Then a day passed, and I got some time to think :)
Right now there are two locations where active circuitry is located: near the lamp for temperature measurement and fan control, and near the power supply for on/off (relay), wireless, dimming and lux measurement.
These two locations are connected via a whole bunch of cables. And I'm already doing cheap wireless at one point. That is just silly!
So the next step will be creating a separate board with wireless for each of those two locations. The only wiring remaining between the two locations will be a 12V/GND cable, and of course the LED current cable.
To be continued, but somewhat further in the future as I'm working on some other things at the moment, and I want to design some proper PCBs for the next step that fit in a nice casing and such.