We had this discussion 3 years ago about the minhogim of when Behab is ‘done’.
http://www.theyeshivaworld.com/coffeeroom/topic/behab-1
In England, the minhag in London is the Jekkisch minhag, other places say it earlier.
But I do find many places are opting out of saying these slichos. I can’t think why it has suddenly become ‘optional’. I was speaking to the Rav of a shul that is officially minhag Hamburg, and they stopped saying it when many people started davening elsewhere on those days. In the case of Yom Kippur Kotton it is only recent that it has become widespread. But Behab is a very old minhag. Does anyone have anything on this?