For most of my time as a UK visa consultant, I'd rarely had cases from EU, EEA or Swiss nationals about what, if anything, needed done either before coming to or once in the UK.
To be honest, aside from some initial worker registration documents for citizens of the 2004, 2007 and 2008 Accession countries for a period of time, or perhaps those bringing non-EU/EEA family members, there was not really anything that necessarily had to be done.
You simply arrived, started studying or working or set up a business or settled down with your significant other - or all of these over a period of time - and you went on from there. For the vast majority of people, no-one thought about paperwork and no-one was compelled to do anything.
With Brexit scheduled for October 2019, where are we now? Will EU citizens need a visa to study?
It's often interesting how frequently patterns and themes emerge in the enquiries we receive at any given time.