You have got a very tight window for staging the event before Christmas. Too close to the holiday and you loose custom. Too early and you will be competing with the all day commemeration of Fred Jordan on 22 November. Any Saturday will be head to head with Cellar Upstairs of course.

Early finish is best in central London - people start heading off for last trains, I have seen gigs where the encore is an embarassment as there is only about a quarter of the audience left.