re PLH/NQY, the times I've flown the route there has barely been a spare seat. The morning departure to LCY and the return in the evening seem to be the most used with less using the return morning trip to PLH and the departure at about 1730. This is due to many using it for a day return trip to London. If there are spare seats, some often book but change their booking at the last minute - you can up to 2 hours before departure with Business Plus - handy if you are in a meeting which overuns. From October the arrival into LCY will be 15 minutes earlier in the morning and about 25 minutes earlier in the evening.
If interested this is my collection of photos from the first PLH-LCY flight in the morning and evening on 20/4.
http://http://s295.photobucket.com/albums/mm123/richardpw/PLH-LCY-PDQ/