Another question concerning NIE's

Hello

A question about obtaing a NIE

I'm English, living and working in France for the last 35 years, I'm now retired (since January 2018) still here in France and I have finally got around to asking for a French passport / nationalisation because of the coming Brexit, but won't obtain this for at least a year as it takes a long time here

Early next year I'll move to Spain for three months so that I can take some serious spanish lessons and look for a place to retire to with my wife, and we hope to move in the next four years or so

My question, should I get the NIE while I'm English and before my three month move ?, should I get it before Brixit is in place as a English citizin ?, should I wait until I have a French Passport and then obtain the NIE as a French citizin ?

To me it seems the best choice is obtain it now , useful if I have a probleme while in Spain for three months, but will this effect me once Brixit is in place ?but I could do with some help in this matter

Many thanks for your help  / suggestions in adavnce

Yours Minty