Run a string of LEDs from the mains

[timmers]

Don't forget that with all these LEDs in series that if one blows or goes high impedance (and they do change with time and temperature) they will all go off. Just like christmas tree lights.

Put say 10 of them in series and use a boost driver like the Sipex SP6691 or similar with current regulation.

8 banks of 10 will work much better than 1 bank of 80.

I have been working with mains voltages for many years and i know how painfull it can be. I will be as careful as i always am when dealing with high voltage

Your'e gonna have to be more careful than that!

Rectified mains is not forgiving at all. -Ask any qualified TV engineer.
Mains thats passed through a bridge rectifier will cause the resultant -v output to be at a half mains potential, and not ground as you would expect / hope.

Good luck.