Big picture: Ceiling LED control
There are a number of constant-current LED driver ICs with PWM control for dimming. You can easily generate a PWM signal from an Arduino, although the IC only has four PWM controllers (so a single Arduino can only control four lights without larger coding effort).

To use these, you need a sensible DC power supply (somewhere between 5 and 12V), which also solves the issue with wiring, as you are using off-the-shelf components on the 230V side. Current carrying capacity on the DC side is an issue though.

I've built a small board for four LEDs once, with up to 1A per LED, adjustable through a resistor divider. I control one of these from an Arduino, and use an Osram OSTAR RGBW LED with 750mA/channel, works fine.



Material cost for the board:


5,96 EUR for the driver IC
1 EUR for the inductors
2,40 EUR for the flyback diodes
1 EUR for the current sensing resistors
2 EUR for remaining smaller parts