Hello. 

The bonnet lock on my ford focus broke. I managed to get the grill off and also have undone the screws behind this part:

However, I dont know what to do now. I still can't open the bonnet. This is the stage I am up to at the moment. I've watched quite a few videos but not sure how to get the bonnet open to replace the parts.

 

From what I know not seen videos of it but the best n normal option drill the key bit out get another lock from eBay with key then fit that but normally it's just left to be done with a screwdriver as it's the plastic long tube bit that gives way..

It's because you've let the lock barrel droop and the anti-tamper has kicked in.
At the back where the lock cable joins to the mechanism (under the rubber cup) is a plastic rod, if it pulls out of the mechanism then the splines won't turn.



Pull the rubber cup off and you should see the connections to be able to click it back together.
I recommend you replace the rod with this aftermarket one which seats more firmly-

https://rover.ebay.com/rover/0/0/0?mpre=https%3A%2F%2Fwww.ebay.co.uk%2Fulk%2Fitm%2F252245489448

Sent from my SM-G965F (S9+)

If you have already taken the two bolts out that hold the mechanism in place then the whole lot should just come up with the bonnet - it might need to be moved backwards towards the engine a bit to get past the lugs, and be careful with the electrical connector which I think is linked to the alarm.  That is exactly what I did with mine and it was a pain but did get it open that way.  Then either replace the white plastic cross with a longer aftermarket one off ebay as said above or what i did was remove the key barrel and cable altogether and I made up a tool which slots right into the catch mechanism to open the bonnet through the grill.