For me, it’s malt vinegar only and I douse both the fish and the chips in it. I’ve never tried curry sauce and I’m not a huge fan of tartar sauce. Ketchup doesn’t work on the chips for fish and chips for me.
Tartar sauce alone ~75% of the time, malt vinegar alone ~10% of the time, both ~15% of the time.
Childhood indoctrination with the old McDonald’s Filet 'o Fish hooked me on tartar sauce. My first experience with fish and chips was H. Salt which introduced me to malt vinegar. But it never fully supplanted tartar sauce in my fishy heart, even now when I eat fancier versions.
I also like tartar sauce on the chips. Though ketchup and malt makes an appearance here as well.
Lemon on the fish, ketchup on both. Ixnay on the artarsaucetay and vinegar. I’ve never heard of curry sauce on it but I’d be open to try that especially if it wasn’t a light brown variety which would look too similar color-wise to look appetizing.
Tartar on both, malt vinegar on the fries. Rather than drizzling it on, I like to break the fries in half and dip the open end into a tub of the vinegar so that it absorbs through the inside of the potato.