Saw a little bit in the paper this morning, quoting Migration Watch UK - yes, the anti-immigration group. Seemed to be saying that the net financial benefit to the UK of immigration is positive - not negative, as they would usually have you believe.
Of course, they *still* try and make this sound like immigration is A Very Bad Thing. Apparently, the financial benefit to "each member of the native population of the UK from immigration is worth about 4p a week - or less than the equivalent of a small Mars bar a month".
The paper I saw went for the "only a Mars bar" angle too, which is not surprising as it makes for better copy than "immigrants give you money".
You can look at Migration Watch's full story, if you wish.