Many countries are trying harder than the UK to get the virus under control. Spain has fewer new cases by a factor of 5 compared to the UK, and has tested twice as many as the UK. It also has fewer deaths in the last few days compared to the UK by a factor of 5. The UK Government may well allow travellers returning from Spain an exemption from quarantine, but more to the point will Spain allow visitors from the UK into their country. The quarantine rule may well backfire on the UK Gov't as so many countries may allow visitors form countries with a poor Covid-19 rate. I notice Greece wishes to set up an air bridge with the UK, if they are exempt from quarantine.