I don't agree we have unlimited resources wasabipeanut. (Excellent username by the way.) Space, housing, school places etc are all at a premium.
Frankly, I'm not really that arsed about immigration. However I believe that we should set a cap on immigration and only allow a set number of people into the UK per year. I do believe it is our duty to be flexible on this number and account for people driven here by conflict in their own county for example.
What annoys me about the EU is that they essentially dictate where we can accept immigrants from. It seems ludicrous to me that someone from Lithuania, a country with whom we have almost no historical relationship, can come to this country almost at will. Yet someone from a Commonwealth country, countries to who we owe a much bigger debt, has to practically jump through hoops and catch a unicorn to do the same.
In an ideal world I'd let anyone and everyone who wanted to live here do so, but as it's not an ideal world I do think Commonwealth countries should get the priority.
The flip side of immigration of course is that it can be viewed as a brain and talent drain. Accepting immigrants from troubled countries might seem like the kind thing to do, but if it deprives those countries of all their talented and intellectual people, is it really the best thing for these countries in the long run?
You can also make the argument that the UK isn't a good deal for immigrants and that they are essentially exploited by us, but that's probably a debate for another time.