Reset Procedure for your key fobs Range Rover 2007 TDV8

Step 1 - setup 'standard conditions'

Key operator in driver's seat
All doors closed
All doors un-locked

Step 2 - initialize BCM to re-sync mode

Put a valid key into ignition lock
Turn key to I (accessories) - this can only happen if the key's RFID is stored in the BCM
Turn key to 0 (off) within 5 seconds (any longer cancels re-sync mode)
Remove key from ignition lock

Step 3 - send re-sync sequence

Hold key at face level (receive antenna is at this height)
Hold down un-lock button, wait till send LED flashes at least twice
Press and release lock button 3 times - the LED will NOT flash
Release the un-lock button - the LED will NOT flash,
If successful all doors will lock then unlock.
Both the transmitter ID and the new (next) access codes are stored in the BCM's temporary memory.

Repeat Step 3 for every key fob. 

Step 3 has a time limit of 30s per key. Over-running any timeout
will part cancel re-sync mode. Remember, ALL keys need to re-sync in the one procedure, 30s each -
if any key fails to sync go back and do step 2 twice (once to fully cancel re-sync mode and once to
re-start it) then steps 3 & 4. Missed keys will be waaaay out of sync.

Step 4 - write changes to BCM permanent memory

Put the key (that was used to start the session) into ignition lock (MUST be same RFID as Step 2)
Turn key to I (accessories) - this must be done before the last Step 3 30s times out.
Turn key to 0 (off)
Remove key from ignition lock
All done. Test all keys.

Note - badly worn conductive contacts or plastic buttons on a key fob can cause the re-sync to fail because they don't make contact, or prematurely release a button, or send multiple presses for one user press, etc. This was where my problem was, but a little bit of "shoe glue" applied to certain points inside the key fob plastic buttons restored clean, clear key presses and the key synced first time.
Besides the plastic button wearing the actual conductive coating that the button presses against the circuit board also wears away over time. There is very little you can do to fix this except by replacing it. The good news is that a replacement plastic sheet with a new conductive contact dimple is included with most ebay button and fob kits.

Note - a key without a RFID chip is still able to unlock the door, but can't start the engine. Useful if the 'real' key accidentally gets locked in.

By-the-way the RFID chip in the key is used by the BCM for all the other luxury touches like individual seat position, outside mirror positions, gear changing preferences, etc.