The Brexit aftermath
It is done. 2021 has brought about the new post-Brexit rules. Britain chose to be considered a "third country" to the EU since 1 January. So any brits that wish to come into the EU now have a new set of regulations to look forward to. At this moment more than 360,000 Britih residents are registered in Spain.
British tourists
Even if you own a second home in the EU, unless you have taken residency you can only spend up to three months of every six here.

UK nationals will need a visa for stays of longer than 90 days in the EU in a 180-day period.
EU pet passports will no longer be valid. Pets will still be allowed in the EU, but it will be a more complicated process as owners will need to obtain an animal health certificate for each trip they make.