some anecdotal in here
https://www.ukclimbing.com/forums/t.php?t=607181
From the AA
Deliberate
AA flood rescue crews report particular issues with some 4×4 drivers who deliberately ignore or move road closed signs.
Darron Burness concludes: “Not only is it illegal but, if you get stuck, your insurer may well reject any claim, which would be a rather embarrassing one to explain.
“You’re also potentially diverting the emergency services from a genuine emergency, so think about your actions – there are simply no excuses for driving into flood water.”
Related traffic offences
£50 non-endorseable Fixed Penalty Notice
Disobeying a road closed or any other traffic sign is neglect of traffic regulations (e.g. give way, roundabout vehicle priority, box junction road markings etc) punishable by a £50 fine.
£100 endorseable Fixed Penalty Notice
Splash a pedestrian or other road user could be deemed careless driving (e.g. tailgating, middle lane hogging etc) attracting a higher penalty of £100 and possibly three points on your licence.
http://www.theaa.com/newsroom/news-2014/aa-calls-for-review-of-flooding-signage.html