Mrposhman: EU and EEA citizens do not automatically receive a NINO (National Insurance number) but will automatically qualify for one once they have registered for either a job, jobcentre, or benefits. You can look-up these, non-EEA immigrants, and the general process here:
workingintheuk.gov
Last month, a new, controversial, Blue Card scheme has been touted to attract the top talents to the EU from around the world, though the UK has an opt-out.
Source
The border control debate becomes ever-more interesting with the Scottish problem. As matters stand, there is no border with Scotland, yet in recent history they have had a nett decrease in population up to the last two or three years.
Scotland has increased its numbers, slightly, due in part to its 'relaxed' welcome of migrant workers. Of course, this also allows an easy route into the rest of the UK.