Friday evening is when I go and they're spot on then. Difference between the two is Summer Lane is your standard modern fish "bar", lots of chrome, two types of kebab, two sizes of fish with too much batter, average food, most modern fish shops are like this. Tunstall Cross is an old-fashioned chip "shop", no kebabs, one size of fish, lightly battered, much nicer. General rule is if a place does kebabs the fish and chips won't be that great. Marina in Parkgate mentioned in another post above is another good fish and chip shop as is Sea Fish in Conisbrough who do the best batter, these are both restaurants but they also do takeaways.
Sorry only ever go the Codfather in Athersley/ New Lodge if I get fish and chips - quality food in there
Try longfields chippy on croft road S74 9hh better than Tunstall Cross just, but in Hoyland keep it local.