Nicholas - Please don't be put off by TopBunks unfortunate attitude. He claims to be a Captain, which is very doubtful.
Unless one is familiar with local geography it is very difficult to know exactly where North is and if aircraft are turning it makes things more difficult. It is also very difficult to estimate the height of an aircraft from the ground. Large commercial jet traffic in that area heading northish around 5000ft was almost certainly outbound from Heathrow.
Grasscarp... The speed readout is probably groundspeed, which varies depending on various factors, not the least of which is wind. If you were flying you probably would not notice the sort off effects you see on those readouts. "Standard" speeds are about 210kts off the stacks and downwind, reducing to 180kts on base leg and around 160kts on final approach to 4 miles from touchdown after which speed is reduced. The actual speeds are varied by ATC for the best spacing on final approach to produce the highest landing rate for the condtions prevailing.