I'm English, and although it's not exactly like the real McCoy, this is about as authentic as you can get in the bay area. Not only that, the prices are very reasonable - $2.50 for a large portion of chips. They will put loads of salt and vinegar on for you if you ask them to as well. Owners are very friendly. It's in the Tenderloin, not a great part of town, but it adds to the atmosphere. If you get take out, they'll wrap it up all yummy in paper for you. They also stock San Francisco's own Pearson Root Beer and Cream Soda, excellent stuff. The fish they serve is good quality, and they also have onion rings, fried zucchini, and squid among other things. Definitely not for the overly health concious, but a great spot and some of the best fast food in the city!
Pros: Authentic, Salt and Vinegar, Friendly