It turns out that switching it off at the mains / unplugging it is not enough to reset it. I held down the start program button (next to the flashing green light) for approx 10 seconds and it gave a long beep and reset. It's now successfully ran through a full cycle with no leaks!
I have an ikea whirlpool dishwasher dwh b10. The green power light is flashing 2 times and it's beeping when closed, which I read indicates a flooded base tray.
Right enough, I opened it up and the base tray was flooded. I soaked this up and have left it over night unplugged, but it still has...