Peugeot 405 radio removal - stuck half way - HELP!

I have recently got a 1996 405 GLX Auto Estate and I wanted to replace
the stereo. I worked out how to remove the stereo from this excellent
site http://www.carstereohelp.org/stereor...ot405UKStr.htm

However, the radio only comes out about half way and then no more. At
this point, the power goes off, so I would image the wires are being
pulled tight/out. No matter how hard I pull on the unit (and I mean
hard), it will not come out. Does anyone have any ideas how to remove
it?

I don't have the security code, so now if I push it back in, I can't
get it to work anyway. So I'm now wishing I hadn't touched it!