Where you'll need to show you've got proper funds to be living there, including health insurance (which won't be cheap for 70+ year old pensioneers in Europe!) - in fact they increased those requirements last year if I'm not mistaken

It's quite common for many countries to demand health insurance (private one) when giving visas (and much more for long term resident visas) to travellers, with age often being the discriminator. No (sane) country will welcome old people that will cost them lots (in the health system) but won't be able to pay for it, unless they have to. Which EU countries do. But since the UK isn't anymore, any UK person wanting to retire in Spain will face much stricter (monetary) checks. If you can "just get along" with renting/buying that nice little flat in Southern Alicante, and having some 400€ for food per month on top of it after all costs, you'll most probably NOT cut it anymore if (future) health costs are added into the calculations.