Don´t want to put a damper on things, but what a lot of people don´t understand is that Spain has more unemployment then the u.k.
Also the Spanish look after their own first
If you have a skill can speak the lingo fluent it may help or if you are looking to go self employed i think you have to find that very special niche that nobody is doing, but be warned if you do something and you are not paying in to the system they will come down hard on you.Also being self employed look at how much you have to pay out every month taxes IVA Assesor fees etc it´s not cheap over here .
Also be aware that depending on where you live you cant run a business from your home.
Also if you have proffesional certificates from the u.k you should get these translated into spanish and certificates will be issued, but do they do say that you will get a lesser grade certifcate then the u.k, (though i have never heard of anybody doing this) also registring your proffesional certificates can depending on your proffesion could take up to a year to get.
Of course this all depends on what you want to do.
I know in our town the police are having a crack down on companys where they are going into companys and asking to see workers contracts NIE´s in bars they are looking to see if people handling food have the correct spanish certificates to do this work.
So all the best and let ALL of us know how it´s going