Yes , we have what is called the Stonecat which is under 16 inches long and can be bought online by North American Native lfs (Jonahs, Sachs Aquaculture, later in the year Zimmermans fish);......we also have Snail,Flathead, and Spotted Bullhead which are hard to find but all get under 16inches and could live in a pond. Our Brown, Yellow and Black Bullhead get 18-24 inches and are quite common, I am not sure what the laws are on exporting these fish to Scotland, but you may already have Stonecats and Spotted Bullheads owned by catfish enthusiasts on the Island....I would check planet Catfish to see.