Electrolux Zanussi WJD 1257 W door stuck?

I shoved in some towels to wash, closed the door, switched on the machine, set the program and pressed start button but nothing happened.

I noticed the door was locked (LED on) and the LED near the start button was flashing.

I've power cycled a couple of times with no success.

This happened before, and when it happened I switched the machine off, came back to it a couple of days later and it was working as expected, but I've got three loads to wash today and don't want to wait two days or so this time.

I've heard about the Diagnostics mode after searching on-line when this happened before, but I don't know how to use it to diagnose the problem, or to reset the system (if possible).

Anyone able to talk me through, step by step how to see what might be wrong? It's awkward to get to anything but the front of the machine due to it being in a tight hole next to a dishwasher, but I will bring it out if I have to, but obviously if there's anything I can do before it gets to that stage, that would really help.

Many thanks,

Simon