Right, I've just been out and checked (completely forgot before). Lock the car with the remote, give it 10 mins or so for the interior sensors to settle, unlock the door with the spare and put key in ignition and turn the ignition ON. There is no need to start the car, just turn ignition on so the lights on the dash light up. Voila, alarm doesn't go off!
The central locking on mine does work with the key, one turn and back to rest position opens the drivers door only, turn again and return to rest position opens everything.