Buy some removal key from Halfords for a fiver, or read one of the many messages below on this very subject.
Cheapest way is to remove the centre console which allows toy to see how it is secured and then release it. A few blunt knives and a lot of swearing also works
put the keys in you got from halfords make sure you push them in far enoug [you should here a little click] then slite your hand ut the bach of the console untill you feel the head unit and give a push then pull the keys then hand and push etc its a realy easy unit to extract just needs abit of for thought, get your head up the back of console with a torch to se first if your not sure, good luck
I agree, they can be a bastard. have removed loads in my time, Clarion would not budge. Even got the tools stuck, drove around for a few days with them sticking out of console. Obviously try the tools first, you may be lucky, but plan that you may have to take console out.