The Visitor rules that have previously applied to non-EU nationals remain broadly the same and now extend to EU nationals.  The Visitor rules enable people to enter the UK for a range of short term non-substantive and unpaid activities such as attending job interviews and meetings, site visits, signing contract, attending conferences, some intra group activities, visiting family and friends, and certain scientific and research activities.
Recent changes to the rules include allowing visitors to study at an accredited institution for up to six months (effectively enabling short term study as a visitor), removing the requirement for volunteering to be ‘incidental’ to the main purpose of the visit, and allowing academic visitors who are experts in their field to extend their stay in the UK to a total of 12 months.
EU nationals will be treated as non-visa nationals, meaning they do not require a visa in order to enter the UK as a Visitor.