Trouble getting the driver door to lock

It's probably the door lock actuator that is failing on you, those newfangled plastic things wear out and with too much resistance it will refuse to do its job. Try locking it with the dash button a few times (let's say ten times of switching between lock and unlock) to make sure it's really not working. If it doesn't work on the button then you want to check the wire for a signal going to the actuator to ensure it is being told to lock. If that seems okay, you've got the fun task to find a door lock actuator for a reasonable price, my suggestion would be the breakers, a new one from the dealer will set you back a fair amount. Then again nobody ever said owning a Land Rover was cheap unless it was in jest :-)