key fob / alarm?

i have a ford fiesta zetec s 2001.i noticed the key fob was taking a while to unlock and lock my car, i was having to press the fob several times to get a reaction from the car. now the fob has stopped working completely, i have changed the battery but it is still not working. i have opened the car manually and the alarm goes off every time so i cannot drive it. how can i get my key fob working again, i have been quoted prices of around £450 to buy a new key fob, surely there is a cheaper way to reprogramme the car. any suggestions??
please help!