It's some races/countries more than others that people want to avoid, and I'd say often people want to avoid a group of int. students rather than the individuals themselves.
Just as when Brits go abroad they tend to stick with other Brits, or at least native English speakers, a lot of international students coming to the UK will tend to stick with their own race/nationality a lot, which means if you end up in a flat of 8 with 3 Chinese people, there may well be a big divide between the two groups. Not necessarily any aggression between them, but being left out because you don't speak their language in your own country can be quite distressing for people who expected to make close friendships in halls.
There are also people who complain about the foods international students cook, particularly people from various Asian countries. As long as you store food hygenically, it doesn't matter what it looks/smells/tastes like, but I've heard of people leaving strange cuts of meat dripping over the rest of the food in the fridge, not wiping surfaces down after cooking etc.
What you personally can do is greet all your flatmates straight away, not bring friends from your home country around every night (once in a while is fine, as your flatmates will do this too) and take over the communual areas, and make an effort to speak to your flatmates even if you make better friendships with people from your home.
Also, don't take this the wrong way, but if you come from somewhere with very different hygiene standards, make sure you listen when your flatmates ask you to do something because they find the way you do it now unhygienic. International students get badly stereotyped with this, but there's definitely some truth in it when some people leave meat uncovered, loos unflushed etc.