09R at Heathrow is mainly used for take-offs. Until recently, some BA and VIP or cargo aircraft used to use it for landings at less busy times, but ATC have severely curtailed this. Even Air Force One has to use 09L for landings now!
If you want to take photos here, it is possible to get them taxi-ing out and lining up, and there are two places.
Just south of the runway, near the end, there's a petrol station and from the stretch of road opposite you can get them on the taxiway by poking your camera through the fence. You can get them on the runway too but this is more difficult (because you're trying to pan the camera through a fence!). I suggest you go to the cargo end where the ground rises slightly, but I strongly suggest you bring along a cheap plastic stall that you can stand on that gives you an extra foot in height - there is a solid panel at eye level which you must overcome! They only cost £2 or £3 and are light and transportable. Anything taller or brightly coloured could be bad news or you'll stand out too much for the police. Good through the middle part of the day here lightwise.
You could also point your camera through the bigger holes in the crash gates to get them turning on to the runway. Problem here is that there are only two or three spaces (so its not good on a popular day) and the grass often gets a bit too long and cuts off the lower section of the aircraft's tyres. Light is best here afternoons, as you are facing east. These crash gates are in line with the end of the runway - just follow the road round.
09R is not too far from the Cargo area and you can catch the bus to here, getting off just as it leaves the airport for Stanwell, its near a petrol station. Alternatively, catch the bus to Longford. The walk is about the same.
Note that on 09L, there is a grass area by the perimeter road, but across the main road, there's also a field, which is more popular with photographers.
Any more, let me know..