I have a Bosch WFK2801 front loading washing machine.

The unit is currently refusing to do anything (pump, spin,fill) just
flashing up error code 06, along with the first 2 LEDs after around
30s of power up.

I *think* error 06 is a door lock problem.

When I apply power I can hear a click and the relay is engaging -- the
door cannot be opened, so perhaps this is some kind of sensor problem.

But before I dismantle can anyone confirm or suggest any alternatives.

I've already done the usual cleanout of the waste trap, narrow pipe up
from there, and the hex-shaped pipe from the pressure vessel to the
pressure switch.

I've not yet cleaned out the pressure vessel.