Illegal Immigrants: What should be done about them?

Immigrants…a tough and controversial topic. It’s very easy to stray into extremism and racism as people talk about it, something which I wholly don’t condone at all. However, taking a look at the topic, are they welcome?
In the US last year one million Mexican immigrants striked in protest, it was said if that strike lasted for another week the American economy would’ve been nearly as bad as it was after the 9/11 terrorist attacks on the World Trade Centre. No one can argue the fact that illegal immigrants do the jobs which we don’t particularly like to do, and to be honest probably better. There’s also a number of skilled immigrants who work in hospitals, universities and businesses. But do we really need them? We have a 1.66 million unemployed people in the UK (Source: http://news.bbc.co.uk/1/hi/business/6904161.stm) Also do we really want immigrants working in our hospitals? No one can deny that they might do a very good job, but at the end of the day it’s making life harder for British medics finding a job. Then again it’s very useful to have a wide range of language speaking doctors from various backgrounds working in a hospital.
Then again If you look at the terrorist foiled two weeks ago, nearly all of them were doctors who were refused admission to work in Australia, which has a lot more hardliner view on immigrants. Everyone also knows there is a lot of terrorist operatives working in Universities to try and hook in young students to whatever their cause may be.
So how should we deal with them? On the downside they’re taking away British jobs and not paying any tax. On the upside we may just need them! But they need us more than them.
Should it be our right to send a woman, who in about two hours time is being deported back to Iran to face the death penalty? Should we be a safe asylum for people facing intolerance and cruelty in their homelands? To some degree I say yes, of course you must look into the case why they are wanted dead in their own country, but for those who are facing death because of who they are and not what they are done I feel we should provide for them. In PMQs yesterday Gordon Brown will look into the case, and I pray to god he can see the reason to let this woman a) live in this country and b) live.
I feel that we should refuse entry to those who:
i) Don’t need it
ii) Are of no use economically to the UK
iii) Are a threat to the UK
iv) Left their own country because they have committed a crime which goes against UK law as well.
I think we should let those in who are useful to us, and deserve the right to practise their religion/profession without the threat of maljustice in their own country. What do you think? Should we have open borders like Europe? Or semi-permeable borders like the US (allowing some in, but not others) or completely closed borders like we have now?