How do I fix my bonnet catch? 2004 Mondeo 2.0 LX TDCI ?

Lock under Ford badge, first turn of key partially releases bonnet, 2nd turn is supposed to release it completely, but doesn't fully turn. Garage can't open it, suggest breaking grill to get at it! Anyone else had this prob?
Car in good nick, only 18k miles done, no accidents or knocks which could have affected lock.