Perhaps the biggest downside of living in Spain is having to actually work in a physical job in the country. Compared to the UK work conditions are not excellent in Spain, conditions described in work contracts are often not met, and many bosses expect workers to work weekends, bank holidays and other inconvenient days without extra pay. Shifts tend to be very long and workers are often expected to work without proper eating or rest breaks.
If you do not really need to rely on going to work in a hotel, restaurant or similar job to earn a living, Spain is probably one of the better countries you can choose to relocate to. The weather is excellent and there are many outdoor past times to enjoy such as water sports, golf, cycling and hiking.
Locals in the country are generally very friendly towards expats providing you make some sort of effort to fit in with the local community. Even if you do not speak the language, Spanish people tend to be very generous in trying to understand you and most are happy to practice their English when given the opportunity.
To sum up, living in Spain is a good idea if you have the means of supporting yourself, at least for some time, because finding a good job is not easy. However, you can expect to enjoy a more laid-back less hurried lifestyle than is typically experienced in the UK.