http://www.wildfowling.com/puntgun.htm
What sort of info are you after? John Forsey was the place around here to get big wildfowling guns, but havent been there for a while
http://www.johnforsey.co.uk

Theres bound to be a proper wildfowler or two around here, unfortunately I only shoot inland. BASC also have lots of fowling info as they were originally the Wildfowlers Association of Great Britain and Island (WAGBI), and own at leat one punt and gun setup.