Try this, remove the top (3 screws at the back push lid back about an inch and lift off) Find the pressure switch (a round flat object with wires and a hose connected)should be by the timer, pull the hose off the switch, if it clicks then the pressure chamber is blocked.The door will now release but you will have to unblock the pressure chamber which is at the front of the drum and involves removing the front panel.
casper...http://www.selfix-uk.co.uk, November 2008