i had the same problem with mine cable was seized had to replace it at a cost of of £5.
to release it i had to use a bit force by unbolting the locking mechanisn from the exterior side at the front of the bonnet using a socket set. a good local garage will know what to do. it will only take 1 hour to do start to finish.
, dont be conned or fobbed off. good luck.
f
firestarter, November 2010