So the dishwasher is playing up, didn't drain on Saturday, though waiting for a bit seems to have worked (there is no water in the bottom after re-running it) without having dispelled the 'error code.'
I'd turn it off and on, but one million points to anyone who can tell me where it is plugged in, because it's not where I thought it was, that's the extractor fan. And nope, not that one, that's the oven.
Having assayed the front panel LEDs and found the little manual to decrypt them, I am pleased to announce that the problem is that the dishwasher has water in it and I should consult my 'after-sales service.' Thanks, appliance.