Actually, I have some knowledge in the area - I'm a foreigner. Eligible to come under EEA rules and work in the UK, however, even then getting a job isn't so simple as many of you make it sound. For non-EEA or non-EEA family members, the chances of legitimately getting in and getting a job are virtually nil unless you make it under the points scheme. Take a look at the points scheme and see how easy it is to get enough points to qualify. It isn't.
http://www.ukba.homeoffice.gov.uk/pointscalculator
I come from the US originally, and people there also think it is easy to come in as an immigrant and that immigrants are taking away American jobs from American workers. This is also not true, particularly in IT. Several years ago, it was easier to get in than it is now - but it was never by any means easy. (I know this from personal experience with a friend who managed to come in on a temporary visa to work for a few years, which took him several years to even be granted).