As I've just done this to install speakers and sound deadening, I thought I'd post my process for others that are looking to do it.
Fiesta Mk6 with manual mirrors and electric windows.
Remove the mirror adjuster cover by rotation it.
Remove the mirror interior cover by pulling at 90 degrees to the door.
Remove the cover and screw in the door latch.
Using a flat head driver, gently lever the electric window switch cover off. I also assume this is where the manual winders would sit?
Unplug the electric window switch by depressing the lug/clip.
Remove the two TORX screws holding the door handle on.
Remove the two plastic bolts under the door card. These do unscrew, but you can pull them out.
Then use the elbow grease to pop the door card away from the door. I found I had to gently lift it with a screwdriver to allow me to get my sausage fingers under it.
Unclip the door lever cable and remove the door card.
There are four TORX 15 screws holding in the speakers.
Remove all the bolts holding the inner door skin.
Next you need to reattach the window switch and remove the foam hole covers for the window mech. Then lower the windows enough so you see the plastic clips that hold the window. There are two. You need to push the clip through the hole in the glass, but be careful as you could chip or crack the glass. I ended up using a wooden barbecue kebab skewer.
You can either remove the glass fully, or just tape it to the top of the door frame like I did.
Remove the window motor plug.
Now the tricky bit, as you have to do this blind.
The device that attaches the inner to the lock has two locating holes and a wedge-shaped locking device.
Moving the plastic away from the door, you can just about get a long flathead driver in to gently lift the clip to allow you to separate the two parts.
This is also the hardest part to get back.
Open the door wide and undo the plug joining the door to the car, and push it through the door, then undo the clip holding this loom to the metal of the door inner.
To undo the loom from the door lock, you need to pull the red clip up, then just yank it off.
Then lift away the panel. Done.
I then wiped down the inside, added the Silent Coat.
Put all the inner trim back on, then added Silent Coat.
Put in the new speakers.
And put the door card back on.
Repeat for the other side.