Well the most common gull round here Jen is the erroneously name Black-Headed Gull, but when I lived on the coast there was Common Gull, Lesser Black Backed Gull, Greater Black-Backed Gull and Herring Gull. I've also seen Kittiwake on the Farne Islands and other sea birds such as Puffin, Guillemot, Razorbill, Fulmar, Shag, Eider, Oyster Catcher, Artic Tern, Common Tern and Sandwich Tern.
On the salt marsh by my school we found Avocet, Black- tailed godwit, Lapwing, Pink-footed goose, Canadian goose, Wigeon, Sandpiper, Dunlin, Tufted Ducks, Pochard, Shovelers, Gadwell, Grebe, Ruddy duck and that big duck that flies to Heligoland whose name escapes me.
Living on the coast and teaching in a school which backed onto a salt marsh has left me with the thought that 'water' birds are quite adaptable as gulls round here (Midlands) don't care if it's fresh water and loads of the waders and ducks don't seem all that discerning either