We've not really got enough room for an unlimited period of unlimited immigration. Not if you want any countryside left anyway.
*weigh
It depended on your definition of 'fairly open', and why is it suddenly only immigrants from EU countries? From an EU stand-point, I don't think it's justified 'changing the rules' for certain EU countries, free movement of people is one of the good things about the EU.
I think I've put your points in the right order.
First point... we're not running out of space in anyway what so ever. In fact we're subsidising farmers to use most of it. I suppose it's good back up for when there's a sudden nuclear war or triffids attack.
Second point... Free movement of people is ace. I was using the new EU countries as an example because that's what I figured I was arguing against, it being the most recent influx. Immigration from any country is good though, doesn't matter if they aren't in the EU.