If you are moving to Spain there are several issues to bear in mind. Residency is just one of them. Tax is another, health care is another but the biggest thing to think about is how positive are you to be able to sell up in the UK.
I live in Spain and come from the UK. It was my intention to come here with my family and integrate into the Spanish way of life. I am a guest in someone elses country irrespective of the EU and my right to be here. Many Brits come here for the weather, the cheap cost of living, and the social life. Many have no intention of learning the language, integrating and becoming part of the community.
I am learning the language. I am now a resident and I pay my taxes in Spain. Health care, if you are under 65 you will need to make provisions in the form of private medical insurance.
The tax system in Spain differs to the UK. There are two ways of being taxed. Either as a resident or a non resident. You should ask your abogado (lawyer) for sdvice on taxes in Spain. They have a tax here which they don't have in the UK. It is a wealth tax. It is better to be a resident but advice should be sort.
Don't come here without doing any homework. The first thing to do is get a good English speaking lawyer to help you through the "minefield" of buying a house and setting up home.
Bear in mind, this is not a good time to be moving money abroad for any reason. The pound is falling against the Euro. In the 5 years since I have been here the pound has fallen by 30 cents to the pound. It was €1.60 to to the pound, now it's €1.30 to the pound. Those are commercial rates. That's almost a 20% drop in currency.
If you intend coming here then be positive and don't be afraid of residency. Since getting residency and learning the language, it has paid dividends by doing so, especially with the local community.