My girlfriend is cabin crew and being the geek I am I like to track her flights.
Quite a few of these sites delay the data they show for security purposes, which may be one reason they disagree,
openATC - quite good, limited coverage, quite a delay in data.
AirNav RadarBox - Screen Shot refreshed Every minute - London aread
RadarVirtuel.com - My latest find and favourite so far covers a lot of area and gives plenty of data - some of the data seems to show planes taxing around LHR.
This one shows data from the last 100 aircraft on final approach.. -
100 most recent arrivals to Heathrow | Heathrow Airport Information