Wow! That is some sea food menu!
Nowhere in the UK is more than 75 miles from the sea but fish is not a nationwide phenomenon. Fish and chips, which if you are lucky, offers cod or haddock but often offers something nameless from the far east which tastes awful, is the norm. There are specialist fish restaurants at coastal resorts such as Rick Stein's in Cornwall but more often there are only the sort of "joints" that you visit once only.
I love fish in all its forms but I am something of an oddity. Talk to anyone and they'll say they don't like fish. The specialist fishmonger that used to be in all towns, even small ones, are few and far between and as a nation the English don't seem to understand about good fish. If you are lucky you can buy frozen prawns, squid, etc. but rarely fresh. We are very lucky in that we have a greengrocer's shop in the village where Horse lives where the owners are keen on fish and go to the wholesale fish market in Manchester every morning at 5am to choose what is particularly good that day. They had swordfish yesterday but I already had dinner organised.