You may not like it but the most respected international measure of corruption levels is that run by Transparency International. That shows that the UK (17th place, rating 7.7) is generally considered less corrupt than Spain (31st place, rating 6.1).
Truth is that neither society is perfect. Where I believe there is a particular relevance to this forum is in the respective property markets. In the UK it is generally accepted that your lawyer will act on your behalf and any properties that are bought or sold are legally built and verified to be so. This appears not to be the case in a small percentage of transactions in Spain.