i understand your frustration, i work for a handling agent at NCL that handles Thomson and used to hand Thomas Cook.
Predicting a flight delay isnt an exact science, there are many factors which can change the estimated time of arrival/departure, what annoys a lot of airport staff is people who expect an aircraft to be made available at the drop of a hat, which is just not economicaly possible for any airline, to have an aircraft sitting on the tarmac ready to fly at the drop of a hat.
btw. Thomson and Thomas Cook are two seperate airlines, ThomsonFly are part of the Tui Group whereas Thomas Cook aren't.