Ford KA Fascia for CD player doesn't fit - trying to replace cassette radio?

I am trying to replace the cassette player on my 1996 Ford KA with a nice new CD player - I have bought everything I need but for some reason the fascia seems slightly too small for the space where the old one went and will not stay in place.

I've tried fitting the CD player to see if that will hold it in place but it comes lose and seems very unsteady. The clips don't seem to reach to clip it into place.

Is this a common problem and does anyone have a solution or idea on how to fix this - I really want to fit my CD player as the cassette player has broken and this is a problem I did not see coming.

Thanks