The UK supplier I've been using to get spores and various supplies is one called cylocybe.
They sell spores to lots of cube strains in syringe, vial or print form, as well as other types of shrooms and gourmet ones.
Their grow kits all seem to be pretty good too, and they're constantly improving on them.
Service it top notch. Honestly I kind of hope I get a problem,as they'll always toss in a generous freebie as an apology >.>