Had same problem. Don't be tempted to keep pulling the lever inside the car - it stretches the cable and there's even less chance of it working. Leaning heavily on the bonnet whilst someone else pulls the lever helps but when you do get it open spray liberally with WD40 and do this at least twice a week till you punt the car! Especially during winter. Don't use grease as it attracts/keeps dirt. If your bonnet is locked solid, it costs a fortune to strip out the front of the car to release the catches. Hope this helps fellow sufferers. Meanwhile, central locking intermittant failure not yet resolved.
Megabyte
September 2006