Hi Lee.
You may well have checked the plenums 2 months ago but unless you have cut off the first 15mm on the drain tubes under the car it still stands a chance of getting flooded, this happens because the two little flaps stick together with wet and dirt creating a mud plug thus stopping the water from draining away, add that to cold snaps which can freeze any water trapped in the tube solid then you have trouble.
Do you have the spyhole mod on your car? it sound like the ECU may have gone for a swim or at least got soaked.
https://the75andztclub.co.uk/forum/s...&postcount=396
https://the75andztclub.co.uk/forum/s...d.php?t=125864