Altho a humble pax I think it is worth adding that many major airports delay approaching aircraft but do not use holding as muchas say LHR does. The reasons for this are I am sure those explained here that there is ahuge concentration of aircraft movments in SE England .I belive London as a city has the most air ransport mvements f any city in the world.
Also a very large proportion of the traffic comes from the South or EAst where the airtraffic control boundaries with France Netherlands etc are in terms of the speed aircraft virtually adjacent to the London Terminal Area.
In many other countries the main city is well away from the borders and theres often more space to sort ths out in.
I make ths comment because going to Frankfurt fairly often we fly past the airport at quite a height and contine heading away from t for miles and miles and miles. No holding patern which passengers notice but just a huge detour so ATC can sequence everybody for the runways
Good luck with your project but I think yoare going to find that its no different to the M25 ona friday-two many vehicles not enough space
PB