Just in case it helps anyone..

I had trouble finding basic instructions on how to get the stereo out of my 06 Focus, key orientation being my main puzzle. Here we go in case anyone else is in the same boat:

Buy the 4 flat stereo release keys [got mine off ebay PC5-132]
Slide them with the flat edges outwards into the stereo slots, they should all click into place
Lever the release keys outwards and pull towards you - I found it easiest to do one side at a time