Its pretty quick between the separate F/J check ins and the machines and fast bag drop. Usually, there's just a couple of minutes wait going through the security check. Since its a shared terminal you often find passengers other than BA at the security check. Just get your driver to take you all the way to the end of the Departures ramp.
On board, I wish they'd serve Lunch on this flight instead of Brunch (as they used to when it was a 10.00am departure). I've read that BA are planning a 7.30am departure ex JFK - no word as to whether that will change the schedule for 178.