Who Spain actually suits
Spain is the right call for most British adults moving to Iberia. It is not the right call for everyone.
Spain works well if you have employment income (especially remote, well-paid), want a deep cultural and lifestyle change, are willing to learn at least conversational Spanish, and are comfortable with a more bureaucratic system than the UK. It also disproportionately favours households where one earner can qualify for the impatriate regime (Beckham Law).
Spain is less compelling if you depend heavily on UK pensions still being drawn tax-efficiently (Portugal's IFICI is often stronger for pensioners), if you have significant non-UK investment assets you need to disclose every year (the modelo 720 obligation is real), or if you want to keep substantial UK property income tax-light.
