Did you pick the lock? because to remove the core of a euro lock such as this you need to pick it and turn the plug 90 degrees so the pins aren't binding (you can use the key aswell),
Then only you can pull the plug out (be carefull if you do it this way, a lot of bits are going to fly off)
Best way is to turn the plug 180 degres and then insert someting to hold the pins in place while you pull the plug out, like a pick, but best is a tool like this :
link It helps immensly with the assembling/disassembling process, it's rather easy to make, you just need wire and something a little curved to stick it into.