Richard, net immigration is falling because of the recession.
It is due to people leaving.
Every recession has been the same, and the effect is always temporary.
Actual immigration is still rising.

The birth rate you brought up again is a red herring.
We have the birth rate we have.
If it rises, to control population we can only control entry.

If we really can not prevent and remove illegals, then again we can only control entry.

Most countries do manage better control of their borders than we seem able to..
I suspect our government lacks the will.
A supply of cheap labour suits them and suits the bosses.
The people who suffer the effects are just the urban working class.
If they complain they must be racist and can be ignored.
And their natural champions, the political Left, are complicit.
Shame on you.