Dunnocks were once commonly known as Hedge Sparrows, but they are not sparrows at all. They are a very common species that can be seen all over the Gainsborough area.
Mercer Wood is a good place to see Dunnocks or hear them singing. They are also common all along the riverside, at Castle Hill Wood, at Gainsborough Cemetery, and most anywhere else.
Dunnock (picture from Wikipedia)