The shops I use are Aquatic Finatic just south of Northallerton on the Thirsk road and Chilton Aquatics in Chilton. Neither are that local to me but they're the ones I prefer. I find Maidenhead Aquatics in Strikes in Stokesley to be better than the Stockton one.
Another shop which sells some fish, including quite a few nano fish, shrimps and non-splendens bettas, is the plant specialist Horizon Aquatics in Newton Aycliffe. That's worth the journey if only to see their display tanks.