hi ive got a fiat brava and the barrel went on it so have replaced with another barrel of another fiat brava but now the car wont start have read something about needing to reprgram the key but the thing is i think you need the master key but the master key ive got only fits into the old barrel which doesnt work. what can i do??

what year?
red key/blue key?
if so,you need the chip from the old key and put it in the new key

simplest way is to have a copy made of the new key and use the old key transponder (cut it out) or have it cloned to the new transponder. If its a remote key, just open it up and swap transponders.
Tony.