Good question.
Until recently we could vote in local elections and for an MEP but not in national elections in Spain. We were ( only just) qualified to vote in the Brexit referendum.
The minute we get back home next month we are going to ask at the town hall if we can vote in the omni shambles of Spains GE in April. I suspect we expats will be unable to vote in any elections anywhere in Spring especially if no deal happens.
Why, as a resident of another country, should you* be able to vote here? Surely at some point you will need to decide if you are legally British or Spanish? I don't mean by birth or spiritually, but rather on a practical level as the very act of emigration should forfeit your constitutional rights (not including earned state pensions at the appropriate age as that is a different matter) in the country from which you emigrated, otherwise, what's the point?
Presumably, at some point after Brexit and any 'amnesty' period has passed you'll need to make the decision one way or tother...
*For clarity, 'you' applies just as much to those living here from other countries... Apologies for apparently singling you out, but asking a valid question that I don't believe has been previously asked