I live in the Midlands which has a high immigrant population (from India, Pakistan etc).
These people in the Midlands want to see some local (to India) musicians and dancers so often they invite them over from India to appear in the UK.
So every member of the "band" or dance troupe has to be given a visa.
But often a few "extra" people, who are not in the band or dance troupe, apply for visas at the same time as part of this group of people (maybe fake roadies or fake stage managers or whatever).
So in the end the party of people coming may number say 25 or 30.
But when it is time to go back to India or wherever all of a sudden only 20 people fly back to India, the rest stay here, and overstay their visa.
And as we have so many areas in the Midlands that are almost totally Asian it is very easy for these people to "hide" in these areas and never get found.
Next thing you know they are working, maybe get married, have children, and then we cant ever get rid of them.
Maybe if they had to put up some money "up front" they may be more inclined to go home to get it back.
However if it is only a "small" amount (£1,000 say) some of them may feel it is worth it as they can earn that much in a few months working in the UK.
And as they are not "official" they pay no tax but use the local amenities like doctors, hospitals etc
It seems to me we are fighting a losing battle, and our totally lax immigration policies of the last 20 or 30 years has made it almost impossible for us to find out who is entitled to live here and who isn't.
There are whole areas of Birmingham that are totally Asian, it is very easy for a person to hide out in these areas for years, even decades, and not get caught.
I dont think making people place a "bond" is going to make much difference.
With the population of India over 1 billion, if loads of them keep coming here, I am afraid it is downhill all the way for the next few decades.