...an estimated 580,000 people arrived in the UK as long-term migrants in the year to March 2010
In total, 355,000 student visas were issued in the year to September 2010, about 16% higher than in the previous 12 months
That cap would be set at about 21,700 skilled workers from outside the European Union. That figure does not include employees earning more than £40,000 who are moved by their companies into the UK for more than a year.
That figures also does not include 10s of thousands of Bobs earning £24K for a year, for whom there is no upper limits on numbers and which is likely set to increase massively. Why is that always missed out?

The government also cannot control the number of workers arriving from inside the EEA

Ministers want to reduce net migration to "tens of thousands" a year by 2015.
Yeah, right, mainly by excluding Bobs and anyone else exceeding the numbers target.

BBC News - Net immigration to UK increases