How to change a car stereo

I kept the stereo from my old car when I sold it because it will play mp3/WMA tracks from disc but when I tried to swap them over previously it wouldn't power up. I assumed some subtle difference in the wiring of the plugs so today I decided to have another go:

1. Download wiring diag. from JVC
   
2. Get tools and meter from van
   
3. Extract old stereo
   
4. Notice 15A blade fuse in rear of old stereo
   
5. Look at rear of new stereo
   
6. Notice empty slot for 15A blade fuse
   
7. Wonder if that's where fuse found on floor when cleaning car came from
   
8. Insert 15A blade fuse into new stereo
   
9. Connect wiring plugs to new stereo
   
10. Turn on new stereo - WOW, IT WORKS!!! :-)
    
11. Try to insert new stereo into dash aperture, won't go :-(
    
12. Realise new stereo still has mounting bracket around it.
    
13. Disconnect wiring and remove mounting
    
14. Re-connect wiring
    
15. Try to insert new stereo into dash aperture, won't go :-(
    
16. New stereo has extra bit of wiring harness to convert from 2 multiplugs to one
    
17. Perform James Herriot impression with hand in dash aperture to try and stuff
18. wiring harness into back of hole for stereo
    
19. Gently insert new stereo into dash aperture
    
20. Vigorously insert new stereo into dash aperture
    
21. Shove very hard on new stereo to get it to go all the way into dash aperture
    
22. Replace front panel of new stereo and turn on
    
23. WOW! IT WORKS!!! :-)
    
24. Pick up old stereo to put in box
    
25. Realise Bryan Adams CD still in old stereo
    
26. Swear
    
27. Check for manual release on old stereo, nope :-(
    
28. Swear again, only louder
    
29. Extract new stereo from dash aperture
    
30. Transfer wiring to old stereo
    
31. Transfer fuse to old stereo (no, I don't know where the one that was on the floor went, OK?)
    
32. Eject Bryan Adams CD from old stereo
    
33. Transfer fuse and wiring back to new stereo
    
34. Repeat steps 16 to 22
    
35. At last! I can play MP3/WMA discs in car again :-)