Well I’ve had a look this morning and I don’t need to remove the door card. I just used a thin blunt edge to lever off the plastic guard covering the mirror area of the door.
It reveals 3 torx screws and the cabling bundle. So it should be a straightforward job once the part is in.
There is a hole though into the door space between the door card and actual door when you remove the plastic cover. I will cover that prior to removing the screws as it would be really easy to loose screws/parts in there.
I’ll add some photos when I get round to doing it.
Video of ZS card removal shows the bolts for the mirror. Looks like the connection for the mirror might be by the bolts hence not needing door card removal. That would make it an easy job. My Mg5 hasn't been delivered yet for me to check but I would be surprised if it is that different. Interesting thing about the door card removal on ZS is that the process is almost identical to the astra. I guess there are only so many ways it can be done hence the similarity.
Right I thought I would give an update. I have replaced the wing mirror unit and learning has occurred. The video of the ZS card removal is the same for the MG5. It is useful to watch.
You can lever the plastic cover off the area where the wing mirror unit bolts are located. You do need to take the door card off. Two screws removed as shown in the video and again levering the door card off causes it to pop out.
You need a size 30 Torx bit to remove the 3 bolts, a little screw driver to remove a smaller retaining screw, disconnect the electrics cable.
Replaced the wing mirror and did the reverse of what was done originally. Be careful with popping the door card back on. The plastic door card though flexible is brittle - I have noted a small crack on the bottom of the door card due to enthusiastic persuasion to refit the card. I’lI repair/replace the door card in due course but can live with that at this time.