Hi again... When you changed the batteries in the key fobs, did you get the whole operation completed within Two and a Half minutes..?? If you take longer than this from the moment you opened up the key and lost the old battery contact, to the point when the new battery made contact with the printed circuit board, the key fob will actually 'lose' its electronic identity with the transponder chip in the steering wheel housing. It then has to be re-synced with the car to re-learn its identity, which is quite a simple procedure to do.
Get into the driver's seat, close the door and all the windows. Put the key into the ignition switch and turn it forwards for 2 clicks only, so the ignition is now ON, but you are not going to start the engine. (if you turn too far and get the starter motor, this will not work, the procedure has to be started all over again.) With the dashboard lights illuminated, press the LOCK button on the remote that is in the ignition switch. All the doors should immediately Lock and then almost immediately Unlock themselves. Turn off the ignition, take the key out of the ignition and open the driver's door. That key should now work with the vehicle and with the central locking. If by any chance the system hasn't registered the key properly, you will need to try it again with the same key. Assuming success with the first key, if you have a second key to re-sync, now perform the same procedure with that key in the ignition and then the second key should be synced-up to the vehicle. If by now neither of the keys will still not start the car, there is a further problem with the immobiliser that re-syncing-up cannot solve on its own, and you'll need to dig deeper into the security system.
Good Luck and I hope it all works for you now... Cheers.. Robin