@carorueil
Correct, if you're not in the French public system, they won't give you a French EHIC. But I'm a little puzzled by how you could be in France for 30 years without making some social security contributions.
But, if you're recently retired (and get a public pension from France or Ireland) that should entitle you to get an S1 form. And the S1 entitles you to free healthcare in the EU. This is probably your best option.
I'm not very knowledgable about the Convenio Especial or how it differs from making social security contributions. My understanding is that folks typically make social security contributions (usually as employed or self-employed, but sometimes as students or unemployed). And contributing to the social security system entitles you to public healthcare (and an EHIC). I believe that the Convenio Especial is a separate access to public healthcare system for those that don't make social security contributions and cannot affordably be insured privately. I think you have to be a Spanish resident for a year before you can enroll, but I doubt there are any restrictions (in terms of age, preexisting conditions, or otherwise).
I've read that the Convenio Especial is about 160 euros per month, per person. And I don't believe it includes an EHIC or cover in other EU countries.
Bulgaria allowed us to enroll in the social security system, and make monthly contributions. In our case, as unemployed. This monthly contribution of 20 euros per month is significantly lower than as an employee or self-employed. These contributions entitle us to public healthcare (and, by extension, an EHIC). This is roughly how it works in most of the EU, but with restrictions (the unemployed, or "economically inactive" option is often precluded for new residents). As you're interested in Spain, this isn't really relevant, and I apologize for the digression. :-)
But I find the comparisons interesting, and it's certainly a big factor in why we spend so much time in Bulgaria. I used to spend thousands a year on a private health policy, and it had big deductibles and many exclusions. But it's risky to be without any cover at all. The Convenio Especial seems to run at c;lose to 4,000 euros a year for a couple. Our Bulgarian unemployed option is just under 500 euros per year for a couple... and it's the only one of the 3 options to also get an EHIC. The added benefit of private hospital treatment being covered (let's say 95% ish) by the public system is entirely unexpected (but absolutely delightful). Our Bulgarian EHICs would be accepted in Cyprus and Spain, but for accidents/emergencies rather than elective surgery. And we'd have to rough it in the public hospitals. :-)