Hello,
I wonder if anyone has a copy of Deligne's letter to Looijenga from 1974 mentioned as reference [26] in Bessis' paper Finite complex reflection arrangements are $K(\pi,1)$ from 2006, see http://arxiv.org/abs/math/0610777, and is willing to share it / make it publicly available.
We were recently proving some results generalizing particular aspects of things that are supposed to be proven in there, and we were asked about the historical background. Unfortunately, we cannot really provide an answer since we don't have access to the letter...