Gasax, I've had internet since 1994 and believe me that's exactly what I've done. I'm not new to research. You try to Google any permutation of seaplane, water landings, England, UK etc and you come up with pretty much nothing. The UK Seaplane Association's website has nothing on it except petitions. This is a flying and pilots forum after all.
Lake's are regularly operated out of salt water in both Florida and the Bahamas. Corrosion X, regular fresh water rinses and vigilant repaints keep them healthy.