I went to a savegame from BEFORE I entered the cellar room and that resolved the problem. I found the key and exited in time to miss the skellies. Perhaps I was too slow the first time or it was just a pure glitch?
You can talk them down using Persuasion or you can just kill them again get into the cycle in which you are killing them all over. In case of the latter, just remember that you can flee combat or just teleport out - go to BR's Vault, get their phylacteries and sort them out.
