Where does this thing for pub food come from?

A home cooked pub meal can be a great pleasure. However... These are probably in the minority now. If a pub menu has more than half a dozen items on it, chances are it's pre-prepared by companies like 3663 or Brakes and just heated up on site. It'll be fairly cheap and very average.

A fish supper, however (for that is what we call it where I am from - assuming you're having chips - if not, you get two fish and it's, rather confusingly, called single fish) is not something best experienced in a pub. There's a few that do a decent job, but none that do anything as good as you'll get in a chippy in Aldeburgh, Whitby or Anstruther.

Oh, and use the condiments. It's not meant to be bland. There's malt vinegar, salt and lemon there for a reason.

Also, ignore southerners. Haddock is miles better than cod for battering.