Agree with the recommendation for A Salt N Battered on London Road. Haven't tried Whitby's but I've heard good things about it. The thing is though, folks have lost sight of what good fish and chips should be like. In the 1990's we seemed to have an invasion of foreigners, especially Greeks, who took over our chip shops. They don't cook brown chips, only pasty white ones. And they don't do golden brown crunchy batter on fish, just a thin yellow soggy one. You might wonder why this idea ever took off? Simple! Because they appeal to folks who eat with their eyes rather than their mouths. They always give stupidly large portions of chips (enough for 2 or 3 people) and the fish is usually huge too. Although it's nearly always haddock - and it's often "Y" shaped. The idea caught on and was promoted by a lot of the franchises that you see around the place, like "Admiral" and such places. And that's another point...a lot of these chip shops are part of a franchise - which basically means the franchise provide all the kit, including the potatoes, the fish, the batter mix, the oil, etc., So as a result you end up losing the skill of the individual chip shop proprietor, it's not an individual family recipe anymore, it's mass-produced bollocks. After nearly 30 years of eating this rubbish most folks have forgotten a few basics about fish n chips...
1 Chips should be brown - not white
2 Fish batter should be golden brown and crunchy
3 Fish (especially cod) should have large soft juicy flakes of flesh
4 Fish and chips should be wrapped in paper, then newspaper
5 Fish and chips taste better if cooked in beef dripping
The only chip shop I know within about 15 mile radius of Sheffield that still does fish and chips in a traditional style is Margaret's just off Whit Moor, near Chesterfield. (Bottom of the Dronfield by-pass to some). Here's a link...
https://www.facebook.com/pages/Margarets-Chippy-The-Best-Chip-Shop-in-the-World/172246332889961
They don't use beef dripping though. But their fish and chips are absolutely divine. There's two other big chip shops within 50 yards walk of Margaret's, "The North Sea" being one of them. Another bleedin' franchise. It's usual to have to queue for half an hour to get fish n chips from Margaret's, but you can walk straight in and out of the franchise ones round the corner. Says it all!
One final thing...re the potatoes...
I see you are recommending Maris Piper Tom? I think they're good and just about every recipe I've ever seen for fish and chips recommends Maris Piper as the potato of choice for chips. People need to be aware that the variety of potato makes a huge difference to the quality of the chips. My own preference though is for King Edwards. Especially, "Red King Edwards" if you can get them. They seem quite rare these-days but as a kid we had them all the time. They make fantastic chips.
I did a comparison a few weeks ago as I had some white King Edwards and Maris Piper. The noticeable difference was that the King Edward chips went brown much more easily and came out crispy! Perfect! Maris Piper's were still good though, but I prefer the King Edwards. They also make superior roast potatoes too. Nothing quite compares to a roastie made with King Edwards potatoes. No other potato gives you that crunchy outside and soft fluffy potato inside.
Anyhow... back to fish and chips.