Harrogate 98% pork sausages made from pork, seasoning and sausage skins. They come in a plastic tray half-covered in a black cardboard sleeve with red writing (which specifically says gluten free). Tesco and ASDA do them for around £2.50 for six.
These are so good and taste so meaty that they utterly annihilate all other sausages. They're also superb cold in salads.
They are your answer.