Scenic remote key not working properly?

My scenic 1999 key that controls the central locking as well as the immobiliser only works every now and then. I have changed the batteries and it still only works every so often. The red light comes on when I press the key. So there is power there..... Can I override the immobiliser somehow and just use the key to open the car door and start the engine? Help me please!

Vicki
March 2009