Usual common sense rules apply, no force is required for any of these operations and if something won't move you're doing it wrong. Also I'm not responsible for what you might do to your car...
Firstly the vents. Apologies for the slightly blurry pic, if was tough to get a decent shot in situe. There are two metal clips which you need to gently pull down with a trim tool, or failing that a small screwdriver while gently pulling on the vent. It will slide forward slightly to allow you to work on the second clip. If you are struggling, this is the one time where a second pair of hands can come in useful.
The clip can be seen in the upper right of the pic...
And you can see the two of them clearly here and how they work...
The stereo is held in by the two larger screws. If you ever need to loosen the dash to fit a Brodit clip to an M where the carbon leather dash is too thick to just press it home, loosen the two screws in the top left and right of the where the vents sit and two corresponding ones below the stereo (not seen in this pic)
The wiring block at the rear of the stereo. The black plug with the yellow/red and yellow/brown leads is the one we're after...
This side view shows the rotating clip in its home position. To release it there is a small clip at the top that you just squeeze with finger pressure. I couldn't get the camera angle but it's obvious.
And released...
A view of the back of the wiring block removed from the stereo. The release clip for the black plug is just above/left of the purple/white lead. Squeeze it and pull and the block will come out easily. No force required...
Thus...
This is actually a block in a block, and you need to remove the smaller one from its holder using a small screwdriver to release the clip and slide it out sideways. It's keyed so you can't put it back backwards...
Like so...
The OEM aux kit is supplied in a block ready to go into the stereo, but we have the CD line in wiring so either you will need to move the 3 wires from the kit into the existing block, or the two yellow leads into the new one (which is obviously simpler)
A pic to show the positions of the wires. Remove this block from its holder as per the earlier step.
Side by side before transplanting the wires
A couple of pics to clearly show the wiring positions of the OEM kit
The wires are held in by a metal clip that needs to be depressed with a small screwdriver while maintaining gentle pressure on the wire. Here you can see it partially out
As it pulls out it will likely catch on the clip. You can see the circle on the wiring clip in the pic below in the long slot. Move the screwdriver and gently push down and maintain gentle pressure on the wire and it will come out.
Do them one at a time and place them into their original positions in the OEM aux kit plug and you will end up with this...
Slide this back into the larger holder (it's keyed remember, it will only go in one way)
And then clip the assembly back into the larger wiring block for the stereo...
Refit this to the stereo and power on. As you cycle through the modes you should now have an AUX option as below
iPhone playing spotify through the intravee with an appropriately named tune
MP3 CD playing, everything is working...
Slide the stereo back in, fasten with the two screws, slide the vent back in until you hear the clips engage and all looks flush. Job done!
You can see I've got the lead trailing out of the panel below the heating controls. I'm going to route it into the glove box but it started hailing so I thought I'd come and write this up. I'll add the routing of the cabling at a later stage. Hope this is useful to someone.
