From time to time my boot won’t open. I push the lid up and down and click the button or remote but nothing. I then leave it five or ten minutes and it clicks open. Go figure!
I noticed the lid was getting very heavy to open so I bought two 30cm struts from the local super cheap auto shop and changed them. Thanks to Concept Symetry for the helpful YouTube btw. That was easy except the lid fell on my head. It’s heavy!
Anyway, I then took the cover off the boot lock catchup see what was going on. The two plastic screw things are a pig but do eventually come out with help of a claw hammer.
I tried to grease it and squirted silicon lubricant on it but it was still pathetic re the solenoid actuating so I took the lock off, took the solenoid off, two screws, then prised the plastic cover of gently with a Stanley knife to reveal the solenoid, cogs and threaded actuator. I noted the unit as a Ford part too btw. I lubricated and re assembled the unit. Melted the lid clips to secure the lid and refitted it.
I then realised that the lock works fine if the boot lid weight is negative, which of course it was now the new struts were installed. The solenoid clicked and the lid popped up just a little when I pushed the boot key button!
Hope this helps anyone!

update today
boot firmly locked and won’t open. You can hear the motor trying. Had to take out the rear seats and re examine the lock. Turns out it doesn’t have the oomph to unlock the lock one the car is locked only when the boot is closed and unlocked. I could see the main spring was quite strong and the locking sling inside the lock that’s riveted also provides the same functionality so I removed the spring and viola it works. I’ll probably get a new Hella Motor/solenoid at some point but it seems to have fixed it for now. Never say ever with this car!