Remove the plastic trim on the front of the washer at the bottom and there you will see the filter in the right hand corner.
You need to slowly drain the water from the bottom so get a shallow tray under there and slacken the filter and drain the water from there.
Once the water is out then you can fully remove the filter and give it a good clean out.
Then try and open the door and see if it will open.
If its still not opening then near the filter is a plastic tab. Pull this tab down and it should release the door and allow you to open it.
Try that and let me know how it goes.
Just wondering how you got on with the washer as the question is still open?