i have opcom version 1.45 which says p0089-00 unknown dtc and showing (present, passed and failed) do you think the valve is stuck open or closed?, i took it out of pump to test, switched ignition on and it was chucking out fuel so does mean its failed causing high fuel pressure?First things first, how are you reading the codes? Be aware that Vauxhalls don't work well with cheap code readers, and even some "professional" ones will not pick up all the codes.
You can't take this type of regulator apartThe car will still start and idle with a faulty SCV. Mine actually fell apart with the plunger hanging out of the valve, only being held by the wiring connection. I could still start the car and drive it onto the recovery truck.
Remove the valve and push the plunger in against spring pressure to check it is free to move.