A steady trickle of needy underclass could break Socialism once the masses realize their cut is being taken... how quickly things are changing
The US has managed it all along as a wholly immigrant nation; the immigrants become successful in their second and third generations, and assimilate, so they're productive and no longer needy. This will happen in Britain too, if the economy and the people accept this fate.
The tweaker said this about his illegal Mexican: "His kid went to American school, now he's an American."