Many thanks to all those who have helped with info and details of the huge LARCxv that is in your part of the country. I finally made contact with the owner last week and he came to see me down in Norfolk today. A unique amphibian,originally built for the US army, I have worked on them for 14years and was able to share much useful info with him.
NO, there not DUKWs, much bigger, their 60 seater passenger carrying,used for coastal trips.If your in North Norfolk it's a novel ways to see the coast. Once again thanks, Skylarc.