I found this quite useful.
On 23 June 2016, the majority of the UK’s electorate voted to leave the European Union. “Brexit” will become effective on 29 March 2019 and when the negotiations on the terms of exit have been concluded.
Until then, the UK remains an EU member state with all rights and obligations.
It is important to note that the referendum result in itself has no immediate effect on the nationality, residence or social security status of EU citizens in the UK.