They are fitted with an anti-theft plate, which is screwed into the cross-brace of the body shell, and requires you to remove the instrument cluster, binnacle, and centre A/C vent ducting to access the screws.
Lift up the touch switches from the back edge first, then unclip them.
Undo the screws above the cluster shroud, and behind the touch switches, then pop it out (it's clipped in along the bottom edge).
Remove the lower cover near the pedals, so you can reach up & unclip the speedo cable (you may be lucky & get enough length in the cable without this step, but be aware of it.
If you can, try to bend the centre A/C ducting up out of the way, and using a stubby phillips head screwdriver, undo the 2 vertical screws holding the plate at the back of the radio, to the brace.
You'll then need to try to undo the nut on the back of the radio, to release it from the bracket as well - this is really difficult unless you have tiny hands. A torch & a mirror would be your best allies here!
Once you have removed the security bracket, you need to pop the eurovox tools down each side of the radio (the holes in the side clips are a guide - you can make your own from Sheetmetal, in an "E" shape - but make sure you form a pointed end on the centre bar of the E, as this is what releases the side clips. The bars of the E need to be about 3-4 inches long.
If that doesn't work Coal Chisel