My experience of bmi longhaul is that after a meal and lights out one of the cabin crew comes round every 30 minutes or so with some OJ and water on a tray for anyone who wishes to take one.
This is perfect as far as I'm concerned. I've had similar service from LH longhaul recently - as soon as I woke (with the lights still off) someone was there offering "water, sir?".
A rather more undesirable experience was on a 6-hour overnight flight (no timezone change), departing at midnight. A light snack was served soon after takeoff, followed by lights out. Fine. But at 4am the lights came on and a big breakfast was served. Breakfast was all over in 45 minutes - then they turned the lights off again. Wierd, wierd, wierd.