... The Bead Shop!
There are two that I always go to, the link above is in London on Tower Street, Covent Garden. It is AMAZING. I try and get to London at least once a year and when I do The Bead Shop is always on my list for a visit. I tend to leave the other half roaming around all the other interesting shops in the area as he gets a bit bored looking at beads!
The other that I like to visit is a little closer to home in Aflex Palace, Manchester.