You have to bear in mind that British citizens in Europe are somewhat less affected by UK law, for obvious reasons, than the EU citizens living here. Probably the most important aspects for UK citizens in the EU are healthcare, which in the EU is an aspect of social security, the aggregation of pension contributions and exporting pensions.
I, as a UK pensioner living in Italy, am entitled to receive my pension, but I am also entitled, under EU law, to an annual increase. There is a great concern that that might not continue—the Government have not committed to continue uprating our pensions beyond April 2020. That is a huge worry, because although inflation is quite low, the British pension is the lowest in the OECD countries and has already been devalued by 20% because of the fall in sterling. Not to increase that is adding insult to injury to people who left this country on the basis that they would always get their uprating.