There are loads of ways posted already of how to get into your bonnet, when the key lock doesn't work.

Best one seems to be large screwdriver technique detailed elsewhere. 2 minute job.

Having got the bonnet open. How to fix problem for good? (or do this before the lock fails!)

My answer was to remove the grill and separate the keyhole lock from the grill. Separate the rubber grommet and pull it along the cable a bit.

Get a suitable jubilee clip about 25mm diameter and slide it over the lock, along the cable part,

over the rubber grommet and settling it about halfway along the white tube towards the bonnet catch.

If you look carefully at the white tube you will see half its length is quite thin walled and gets more substantial as it gets nearer to the bonnet catch. Locate the jubilee clip on the weaker part. About 25mm to 30mm from the bonnet catch.

The inner parts of the white plastic tube are able to slide in and out a bit. (This is why the lock fails.) It needs to be located into the bonnet catch. A big screwdriver and a bit of pressure inwards will achieve this.

If you are a bit lost as to what needs to happen here then just take the bonnet catch off and have a look at the way it connects to the lock mechanism.( 2x 10mm bolts). Reassemble.

Check the catch is working using the key when applying pressure inwards. In other words the parts are located correctly.

Tighten up jubilee clip carefully until it collapses the tube slightly and grips the inner parts, whilst maintaining pressure inwards. The inner parts will no longer slide in and out.

Jobs a good un.

Only thing is with your solution is it's designed as a anti tamper to stop those trying to get under the bonnet to possibly steal your car otherwise a good idea for those that find this continually happening a pain .