Making sushi in the uk?

I love sushi but the city I live in does not have any sushi restaurants. I want to look into making my own, but how hard is it? and would I be able to find all the ingredients? What kind of fish can I use? would salmon from the supermarket work or do I have to have higher quality salmon to make it ok to eat raw? Bear in mind that I live in a small-ish city without any speciality shops. We do have big supermarkets though