For anyone arriving too early to check in I can fully recommend the pastime of watching passengers with luggage queuing up like sheep to pass through the terminal fire escapes with only single doors open while standings by the side of the proper sliding door entrances that often just sit there closed, as no one is close enough to trigger the doors. Even when they are open because the airlock has two sets of doors at right angles again people just queue up to use the fire exit. The best bit is that the traffic is in both directions so people has to wait for a gap to go in the opposite direction. Signs saying fire exit only are ignored as are the large signs over the main doors saying entrance and exit.
On a more serious note my pet hate are the amount of smokers who gather around the entrance canopies puffing away while standing by no smoking signs. It just seems to be a Luton thing as I don’t seem to experience this at other airports . Maybe it is because of the lower class of people Luton attracts.