Worth trying a pressure switch,.
Does that mean it's still possibly the switch to blame? At only £12, I'd happily give it a go, but I was thinking that the fact the error occurs on a Spin cycle with the pipe disconnected, ruled that out?
I'd noticed what appeared to be a 'Digit Display Arcadia', what I have, online for £56. Would that replace the electronics, if they were to blame, or are you saying there's other kit required to then 'program' it?!
As an aside, if all else fails, what would you buy as a replacement in the quality price brackets you describe? I do realise that the price in pounds of white goods has stayed static over 10 or 20 years, meaning in real terms they've become much cheaper, and seemingly poorer quality.
One last question. When I registered for my 12 month default warranty, they claimed to offer 5 years of free parts cover. Would engineer charges make this a worthless in terms of saving if say the electronics have failed?