Being a northerner I'm not sure I agree with this. Around Lancashire asking for just 'Fish and Chips' would generally be replied to with 'Do you want cod or haddock?', with the popularity being 50/50. Most chippies wouldn't even serve plaice. I'd say the same is true around Yorkshire on the other coast. I agree though the the fish in Seattle is much, much tastier.
Your right about the haddock instead of plaice, remember when I first experienced it in Bradford many years back and got downfounded looks with regards to Cod.
