I fitted a new catch for the tray on my centre arm rest today, so I took a few photos along the way.
I found it easier to take the whole arm rest off but having done it once, I feel confident that the catch could be replaced in situ.
Removing the arm rest is just two screws:
Once off, locating the clip that holds the cushioned part of the arm rest is the hardest part. I tried various screwdrivers before realising that it must be quite thin.
Note: This picture shows the arm rest with the metal runners removed. You can see the metal clip that has to be depressed by sliding the thin screw driver in as shown on the previous photo.
Once released, slide the cushion part towards the front of the car and it will come right off. Remove the two screws from the tray hinge:
This upper side will now lift out exposing the screws that hold the two catches:
Unscrew the two screws holding the tray catch, or three screws if it's the main arm rest catch is broken, and fit the new part.
Picture below shows the new catch and the broken catch.
Reassembly is just a reverse procedure.
Whilst apart, I took the opportunity to oil the rear hinge pins for the tray and main arm rest before reassembly.
All good now.