Have flown back from DEL twice in the last 2 months, once in F, once in J (and plenty of other times in the past 4 years). There is little appreciable difference in the ground service for either cabin, save for someone walking you to the lounge and ensuring you get a seat.
My approach would be:
* Arrive 2 hours before - this is enough time.
* Find the BA agents near door D before you enter the terminal. Tell them you are travelling F. They will find you a porter.
* Queue to enter the terminal. Make sure you have a copy of your itinerary or e-ticket receipt to avoid delays. Also have your BP handy
* The porter will take you to the premium x-ray machine (hopefully you won't have to call for the station manager at this point like I did earlier this month after some woeful treatment at the hands of the security staff)
* Your bags get stickered here, and your hand baggage gets its own tags.
* Porter takes you and bags to the F check in. Prepare to queue here.
* Get checked in, get your lounge3 card and ensure you have completed your immigration forms. If a snob, you may wish to use an F tag on your hand baggage rather than the vulgar green effort attached at the x-ray machine.
* Show the man before immigration your completed form, then join the immigration queue. Hint - either side is normally faster, and look for a line being served by 2 agents.
* After this, pass through Customs (no queue)
* Go to the Clipper lounge. Give the staff your lounge card and get a free drink! BA reserve the tables and seats at the back of the lounge. If one of the ground staff escort you in they will ensure you get somewhere to sit.
* That will have taken 45mins-1hour. Put your feet up for 20-30mins.
* ..and then join the long snaky queue for security. It looks long, but normally takes 10-20 mins. Remember those hand bag tags? Important here as they get stamped to prove it has been checked. Also be prepared to be frisked.
* You are now in the departure hall. If boarding has started, have no hesitiations about queue jumping and waving your BP. If it hasn't, force your way to the front, again waving your BP
* Almost there! There is another check of BP and the aforementioned stamped bag tags. This is followed by a random secondary screening (F does not exempt you from this). Finally your BP is collected at the entrance to the jet bridge and you get to join the haven of the plane after the DEL 'experience'.