There is plenty of crap fish and chips to be had in the UK. If you're going to try some, I would suggest getting a recommendation from a local who seems a bit discerning, and then *maybe* you'll get something decent. If they say something like "that place was good the last time I tried it, but they've changed owners since", then that is not a recommendation.
There's a lot that can be done wrong when making fish and chips: a crappy source of fish results in tasteless fish, crappy batter, too much batter, not enough fish, crap chips that have been made with crap potatoes or simply not cooked correctly. Most fish (I've tried anyway) have a pretty subtle/delicate taste already, some have less than that and it goes along with the fish's freshness. IMHO a decent chunk of cod loin is what's needed, but cod fillet is cheaper so that will sometimes get used, then there are several other types of 'white fish' that literally taste of nothing at all IMO, but they're a lot cheaper than cod.
It's a shame that cod is getting over-fished in the UK's locality so I'd feel guilty if I had it that often.