Interestingly, the Q2 results for Spain are actually better than for the UK (-18.5% vs -20.4%). It's only the comparison to the end of 2019 numbers specifically where Spain comes out worse.
Debatable why, plausibly because the Spanish lockdown started earlier in Q1.
Since the entirety of the rest of the article is about today's Q2 results specifically though, a comparison of those would be more relevant. Smells like the BBC cherry picking to try and find anything where the UK isn't in last place.
It's almost certainly because the Spanish lockdown started earlier in Q1 - if I remember rightly, other articles have mentioned that the UK saw less of an economic decline in Q1 than many other European countries precisely because of the timing of our lockdown. Comparing Q1 to Q2 results and comparing countries based on that would therefore be misleading, because it's not measuring actual economic differences but an artifact of how lockdown timing happened to align with our arbitrary measurement cut-offs.
(Also, speaking of misleading, it's interesting that all of a sudden the BBC can correctly compare US GDP figures with European ones now that it's the UK they're comparing with. Previous coverage quoted US quarterly figures that had been multiplied by four to annualize them next to non-annualized European ones, making it look like the US was doing worse economically than other European countries like Spain when it was doing better.)
Debatable why, plausibly because the Spanish lockdown started earlier in Q1.
Since the entirety of the rest of the article is about today's Q2 results specifically though, a comparison of those would be more relevant. Smells like the BBC cherry picking to try and find anything where the UK isn't in last place.