I have two nearby fish stores. One is a branch in a garden centre. Huge range of fish, they do marine fish and the more rare (pah terms) fish such as arrowanas etc etc. But they are too far away but they quite good.
The one I use is Pets At Home, which is very good. Okay, the staff aren't too knowledgeable, but I have books and the internet and this forum. I can do my own research. The fish are always healthy looking and if I have a problem with a fish it is dealt with straight away. (dead/sick fish).
Pets At Home took over all the Petsmart stores in the UK, and it is 100% better since the changeover. I'm not even gonna put imo, because imo it is fact!