What species do all these different places (no pun intended) use? Many 'shops' probably don't even know that there
are different kinds of fish, they would assume there is only one kind: frozen!
I've been told that "Plaice" is best for this dish but I think it's just a type of Flounder.
The problem with getting good Fish 'n Chips around here (mid-continent, Mississippi river town) is getting those fish to swim upriver nearly a thousand miles (it's a really crooked river!) so they can be 'brought near the boats!' But I think the "best" is eaten out of doors in temps down in the high 30's and with a very light drizzle! Almost anything warm will taste better then!