It is the EU who have been unreasonable and vindictive in denying UK citizens the right to vote in

municipal elections in EU countries.
The British government by contrast still allows EU citizens the right to vote in local Council elections. Furthermore, British citizens, living in EU countries, are still allowed to vote in UK General elections

for up to fifteen years after no longer being resident in the UK. I think this is perfectly reasonable.
After all, if you have not been resident in the UK for more than fifteen years, are you still au fait with
everything going on in your country of origin? British citizens, living in EU countries, are perfectly entitled to become citizens of the country they are

residing in.
The EU is an international trading bloc, NOT a sovereign country.
I think the French, in particular, will demand that British citizens become French citizens, before they agree to allow
UK citizens to vote in French municipal elections.