Immigration is a difficult issue; we need enough people who are both productive and compatible with our culture, in order for the country to function smoothly and to keep population levels up to a viable level.
As a civilised country, we also have a moral obligation to offer asylum to a sustainable number of those who need it, providing they do not have a harmful effect on society.
Whether 'compatible with our culture' is a bit iffy or not depends on how we want our country to look in the future. If we want it to be more or less as it is now, we need people who will integrate and adapt to our ways. If we don't mind change, and/or a fragmented society then that is not important.
Of course, change is not always good - I feel that we're doing quite well as a secular society with broadly Christian tolerant values. If enough people with strongly held views based, say, on a different religion settle here, it is inevitable that they will maintain their identity and begin to exert an influence. There is now a fair degree of power in the 'muslim vote', for instance, and it's arguable that we now effectively have blasphemy laws.
As climate change worsens, there is likely to be a large increase in the number of people migrating from, say, Africa to northern Europe. Either they all have to go somewhere, bringing significant societal changes to their host countries, or they must be denied entry, neither of which are appealing options.
Nothing racist here, if we differentiate (as I do) between race and culture, although obviously most likely immigrants will be brown, but others will, of course, see things differently.
Interesting times.......