Relocating from France to Spain

Hi Jan
I was in exactly the same position a year and a half ago. And like you, I had my Titre de Sejour since 2002. But after the brexit vote, I got all the necessary together and applied for Citizenship- it's a faff, but eminently doable. I was granted nationality at the end of 2017. My wife's is also being processed, and should be done soon
But because we bought a property here in March last year, when the brexit Transition period was still in force, we actually successfully applied for residence here using our Brit passports, pension payments etc
Unfortunately for you, with the transition period having ended, the hoops they are requiring Brits to jump through now to get residency are substantial. You can google them
If I can give you one piece of advice whilst you are still there and have a French address, apply for citizenship. If you have been there 19 years and can show financial means (plus a few other beaurocratic hoops), you will be guaranteed acceptance. Just keep shtum about moving to Spain for the moment!
Because once you are a French citizen, you then become a full European citizen again, with all the rights to travel, live and work where you want in the Schengen area. You can spend as much time in Spain as you like, and if you want to become officially resident, the process is really easy compared to how it is now for Brits
I wish you well
Alan

I agree with Alan: before moving from France, you should make sure you have formalized your right to residence in France, either with a French (= EU) passport OR a French permanent residence permit.

After so many years there, I agree that you should be entitled to a passport. But, perhaps, for patriotic reasons, you don't want one. After "almost 19 years" there, I would be very surprised if they would make it difficult for you, even now that the transition year is over. (In fact, I would be rather surprised if you did not already have some kind of paperwork that evidenced your right to permanent residence.)

It's probably easier to stay in your current home while you do this, but if it's necessary to sell up now (the sale is already in process, for example) then simply rent somewhere so you have a rental contract to provide in support of your application.

A permanent residence permit issued in an EU country is supposed to be almost equivalent to an EU passport, and grants you free movement rights to live/work/retire in any EU country you choose. Personally, if given the choice, I would go for the passport... but it's a matter of personal preference, and it should make little practical difference.

Wherever you relocate to in the EU, including Spain, you should still apply for a new residence permit in that country, but it's very easy compared to doing it as simply a British (=non-EU) citizen.

I would say it's a mere formality, if you can demonstrate your right to free movement in the EU (with either your French passport or permanent residence card). The usual paperwork you provide is: a proof of address (a rental contract or deed/Nota Simple for your new place in Spain), proof of financial means (your pension), and proof of medical cover (usually a Spanish insurance policy, or possibly they might accept your French EHIC card, or your UK S1 form, if you have it).