There are halal butchers 15 minutes from campus in Hyde Park. There are many Asian supermarkets eg. Maumoniat, there's a big one with a butchers inside it just across the road from Maumoniat, jsut ask the guys in there. Almost all the takeaways are halal.
I don't know about a big Asian community WITHIN the university, it seems that there are more serving the university population than IN it, if you see what I mean. There are Asian/Indian sub continent students who are international or Masters students, but I don't know how many Muslim/Asian students there actually are at Leeds - I haven't thought about this much before, but its true that hardly any of my classes have Asian students, perhaps its because of the subject I study!