https://www.theargus.co.uk/news/17953510.drivers-cold-fined-5-000-purposely-splashing-pedestrians/
This article seems to suggest that drivers can be fined up to £5000 for splashing pedestrians - well.. technically they can but Lucinda Dore has represented many drivers over the years and never one for splashing!
Here's what the law actually says about careless driving/ driving without due care and attention...
https://www.ldlegalservices.co.uk/driving-without-due-care-attention