to remove the radio (non-idrive), follow these instructions.
To take out the radio, you will have to remove the element with the heater and a/c controls in it first. This is fastened with two clips on the sides:
1. take an old creditcard (or something similar) and bend one (short) side of it in a 90 degrees angle.
2. insert the card between the radio and the a/c-controls, bend side first.
3. move the card to the upper/side of the a/c-controls and pull it, making sure its bend side hooks behind the controls.
4. the a/c control unit should move forward a bit. Repeat step 3 for both left and right side.
5. you should now be able to pull the a/c controls forward.
Personally, I went through all suggestions, and I can report that as for my 2005 non-idrive E90 the trim tool/bent credit card approach does not work at all. Not even removing the glovebox did the trick.
The thing that eventually worked was to first pry carefully the plastic AC cover panel below the radio, revealing the two slots or thinner sections of the upper edge. At those points, you should be able to see the plastic clips that attach the cover panel to the actual AC control unit. Once those are undone with a suitable tool (wooden stick from a cheap ice cream for example), you can progress to the side clips. You don't need to undo all the numerous clips to remove the panel completely, only so that the metal spring clip on one side, keeping the AC control unit body in its place, is visible. After that it should be pretty straightforward.
Two weeks of prying and twisting before that got me nowhere. However, I managed to keep all the parts and clips intact despite the rather liberal use of force on the way!
I hope this helps someone else on the exciting journey to behind the AC panel