Where do I buy sushi and sashimi in Edinburgh? (NOT restaurants)?

Is there anywhere I can buy sushi and sashimi-grade fish in Edinburgh?

I'm not talking about restaurants, but rather, Japanese supermarkets or food stands... where I can buy stuff and take them home to prepare and eat?

Preferred price range: sushi for under £2 and sashimi-grade fish meat for under £7. (And, come on folks, I've already upped the prices... in Japan - which is pretty expensive too - I can get this stuff for 2/3 of these prices. Anything more than that would just be exorbitant. And, as I said, I am NOT talking about restaurants.)

It's fine if I can save money by purchasing ingredients separately. Just tell me where I can buy stuff like Japanese seaweed, Japanese condiments, imitation seafood, top-grade salmon (good enough for sashimi), wasabi, etc. etc.

If the prepared foods are too expensive, I can just go ahead and make them by myself... BUT I do need the *ingredients*!!

Thanks in advance! ^_^