I think most of the drivers realise that it is not LHR ATC's fault that we go round and round the hold, at the end of the day the system is being asked to provide more capacity than it has.
What is however very frustrating is to take off from AMS or MAN with no slot, fly 25 mins down the road and be told you have 15-20 minutes holding. Surely the slot allocation system can take forecast load and slot departures accordingly. It costs about £50 a minute to keep an A321 in the air so we are talking very serious money here, millions and millions are year. With all the high tech gear in the aircraft and on the ground there must be a way to make things work better than they do.