I've noticed that Chessington's Halloween page
has been updated to show the dates for 2016. As has been the case recently, the event is very short and will run from 21st-31st October 2016.
There also appears to be a lineup on the page advertising three activities: Curse of the Lost Tomb (a family scaremaze from last year), Trick or Treat Wood (a family-friendly walkthrough) and a fancy dress competition. I don't know if this is 2016's lineup or if the list hasn't been updated from last year, but I think it's a bit poor to be honest.