dont forget that for the majority, those that do come over, want to work, are young and dont really need NHS care (being young). This injection of an instant workforce will be a boost to the economy. How? Those 600,000 people need services. Wherever they end up, they will need to buy stuff, use stuff and do stuff. Their presence will create more jobs than they "take". Speaking of which, they also tend to do unskilled jobs. Jobs that few locals will do because it is either, beneath them, or they feel doest pay high enough. The demis of the industrial/production industry is testement to the lack of a local unskilled docile workforce.
So this will apply pressure on locals for job competition. Well, i think that since bosses will hire the most hardworking, less likely to take "sick leave", regardless of nationality, isnt that a good thing for the business?
What you do need to be wary of, is the "professional" immigrant. Those with dubious qualifications coming here and using them, even tho they are not up to UK standard. Those that come here to claim benefits should be equally be chucked out back to where they came from, or their goverment billed for their benefits.
It is time to end this idea of "birthright" to a job, since you're now part of the united states of the european union. That is an unescapable fact, live with it, and adapt, or remain jobless. Competition forces change, improves productivity, drives people to be better. We have been sitting on our arses for too long while the world is overtaking us, time for payback.