I had this problem too. It is due to the increase in radio frequency usage in proximity to your car, for example wireless burglar alarms, wireless TV transmitters and probably also wireless broadband. What happens is that the car picks up a signal, wakes up the car security system to check if it is a valid signal to unlock the doors, finds it is not but then stays alert for a few minutes before sleeping again. There are 2 ways you can solve this: A) Disconnect the antenna from the key fob receiver unit under the shelf on the right (offside) of the boot, the down side to this is that you must hold your keyfob to the window next to the receiver and press the button to unlock your doors, but it is free (This is the option I am using). B) Buy a new receiver unit from Land Rover at over £150, which has been modified to look at a smaller range of frequencies. Have more of a look here http://www.landyzone.co.uk/lz/f10/rangerover-flat-battery-50300.html. Good luck.
Robert, November 2010