unfortunately, ford don't actually list any instructions for the removal of the glow plugs.
They are located at the back of the engine.
First of all, you will have to remove the windscreen wipers, very carefully, and also noting the rest position on the windscreen. Take care when removing the wiper arms, as they are common for breaking.
Then, you will have to remove the scuttle panel.This is the long piece of plastic, that runs across the bottom of the windscreen. Again, take care, as if you are not careful, you can break the windscreen.
Once the top scuttle has come off, you can then remove the lower part. This is held in place with two torx screws. one at either side of the car.
Once you have done this, you will then be able to lean over the engine, and look down the back, to identify the location of the glow plugs.
Make sure that you disconnect the Battery, before removing the glow plugs.
When installing the new ones, be careful when tightening them up. you do not need to go mad, and over-tighten them. This can lead to snapping the glow plug.
The replacement of the glow plugs on your vehicle is not a simple task. If you are not fully confident with the above instructions, i would strongly recommend taking the car to a competent repairer.
Please don't hesitate to ask if you require any more iunfo.