They arrive at Barton cottage in early September. Colonel Brandon's departure is at the end of October. Willoughby leaves shortly after--within a week or two.

Edward shows up about a week after Willoughby leaves and stays for a week.

The Palmers arrive 'soon after' Edward leaves and stay for a few days. Almost immediately after, the Steeles come from Exeter. That would put their arrival at Barton around the end of November. It's perhaps a few days or so until the big reveal, so it might be into early December when that happens.