How can i Fix my Ford Scorpio immobiliser?

I could not get into my car yesterday using the remote control so decided it must be the batteries and changed them. The car still would not open so my partner tried the spare key and we think we may have tripped the immobiliser? Can anyone give me some advise as to how we can fix this? any response is appreciated as we need the car to get home for xmas.

Sarah
December 2009