It's like any food, needs to be done properly with high quality ingredients. Our local one uses beef dripping, sells nothing further outside the fish and chip zone than parsley cakes and closes at 8. People queue out of the door. We have fish (boned and skinned Haddock here, not your southern cod or worse) , fish cake (which uses slices of potato, is as big as your hand and contains nothing shredded or green) and chips maybe every other month.
I lived next to a place in Kingston that claimed to be a chippy. It was run by the same people as the kebab shop over the road and the fish looked like something by Findus. Just more rubbish to soak up beer.
Andy