According to informed sources...
There was a quota of overseas doctors in place (which is why there are, or were, 6000 Middle Eastern doctors here). There's no rhyme or reason for this unless you read it as a Blairite attempt to break the power of the doctor's clique - foreign doctors aren't here as long, can be put under more restrictive controls ('work in this hospital or get deported'), given worse jobs, without complaining as they don't have the powerful support of the generally politically well-connected middle class families British doctors have come from. You can probably pay them less and stop them becoming consultants, too (even more power and money saved). It's a Blairite hallmark that where Thatcher tried to break the power of the unions he took the fight into the professional middle classes.
All this sort of ended last year when the imminent glut of UK doctors appeared on the radar and there was a concerted attempt to boot out a lot of the foreign ones, contrary to a previous agreement that once you were in, you were in. There's a court case about it.
There's a very interesting leaked email on this, where it's suggested that the major reason behind changing the way doctors are recruited was to discriminate against foreign doctors. Naturally, the cumulative effect of this means the foreign doctors are stressed and annoyed at the UK. See the BAPIO website for details:
http://www.bapio.co.uk/