I find it strange that many people in the UK are concerned about the legality of its immigrant population and then object to the security methods employed by the British Government and agencies to ensure jobs and benefits are only given to those who have a right to receive them.
I would also warn against accepting 'Migration Watch' as a fair and independent statistical body. It is merely a more cultured and believable British version of the scaremongering right wing shock jocks found in the USA. They are renowned for massaging facts and figures to appeal to the basest fears of concerned people.
http://www.unhcr.org/cgi-bin/texis/vtx/news/op endoc.htm?tbl=NEWS&id=441a7d714
For every such organization spreading fears of rampaging immigrant hordes, you will find an organization that tells a different story. Read widely and take your pick, depending on your instincts and beliefs.
Best wishes to you all.