Any standard DIN radio removal tools work best. These are U-shaped, come in pairs and normally fit two holes in each side. £3 in Halfords. As mentioned above, bend the U open so it’s L shaped and push the ball-shaped end into the holes in the radio, one each side. (In my case the tool snapped into two bits - even better!). Once you feel them click, push the tools apart a little (left one to the left, right to the right) so they stay engaged in the catches as you pull and wiggle towards you. Once it comes an inch or so out of the dash you can then pull on the case itself.
Anything that fits into the hole and dislodges the catches will work: as above, small Allen keys, small screwdrivers, even standard wire nails - see photos 5 and 6 to see why.
Photos:
- standard tool (one of a pair)
- Bent apart…
- …and (usefully) snapped into two bits
- One in each side of radio (in your case, either side of CD slot)
- Close up of the catch the tool engages with
- Push the tool to side pulls the latch in so the radio comes free