Its not just tens of thousands though, is it? Thats on top of the hundreds and hundreds of thousands we already take every year! "We have so much space here" look at the land mass and population size of the UK and compare it with other major countries, you'll notice we are overpopulated, hence we cannot take any more. All you need to do is go around the country and you'll see it almost everywhere with your own eyes. Also you didn't account for something we need called INFRASTRUCTURE, we do not have the roads, policing, housing, schools, hospitals, waste management systems and money for the people already here. Why would you want to add fuel to the fire of a problem that isn't going away and is only getting worse?