Thank you Dave for the reply!
Is this something I can likely replace myself? The dishwasher is in-built, is this something that will require the dishwasher to be taken out?
As another data point: I’ve turned off the dishwasher overnight and next day it seemed fine. I did another proper cycle with dishes in and the cycle ended with the same error, however the dishes were cleaned and there was no excess water in the dishwasher.
Does this sound like it could be the problem you describe?