Would be great to catch the fish you see in aquariums/shops, though in the UK thats not really a possibility (unles you keep cold water fish or shopping trollies, leather boots or carrier bags in your tanks).
I know in Florida theres a number of sites where people fish for peacock bass, oscars, mayan cichlids etc. They tend to be better specimens than shop bought ones (well from the pictures I've seen I would say so). I also think the university in Hawaii has quite a reputation for aquarium fish in its water ways. Though to be fair, if I was in Florida or Hawaii, fishing for oscars would not be the first thing I would, but it would be on the list